WorldWideScience

Sample records for incoherent radiation fluctuation

  1. Absolute Bunch Length Measurements by Incoherent Radiation Fluctuation Analysis

    International Nuclear Information System (INIS)

    Sannibale, F.; Stupakov, G.V.; Zolotorev, M.S.; Filippetto, D.; Jagerhofer, L.

    2009-01-01

    By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and successfully tested a simple scheme based on this principle that allows for the absolute measurement of the rms bunch length. A description of the method and the experimental results are presented.

  2. Evidence of strong proton shape fluctuations from incoherent diffraction

    International Nuclear Information System (INIS)

    Mantysaari, H.; Schenke, B.

    2016-01-01

    We show within the saturation framework that measurements of exclusive vector meson production at high energy provide evidence for strong geometric fluctuations of the proton. In comparison, the effect of saturation scale and color charge fluctuations is weak. This knowledge will allow detailed future measurements of the incoherent cross section to tightly constrain the fluctuating geometry of the proton as a function of the parton momentum fraction x.

  3. Plasma density fluctuation measurements from coherent and incoherent microwave reflection

    International Nuclear Information System (INIS)

    Conway, G.D.; Schott, L.; Hirose, A.

    1996-01-01

    Using the spatial coherency present in a reflected microwave signal (Conway et al 1994 Rev. Sci. Instrum. 65 2920) it is possible to measure a coherent, Γ c , and an incoherent, Γ i , reflection coefficient (proportional to the radar cross section) from a turbulent plasma cutoff layer. Results acquired with a 17 GHz reflectometer from a STOR-M tokamak edge region (r/a ∼ 0.8) give significant Γ c and Γ i , which suggests two-dimensional structure in the reflection layer. Using a 'distorted-mirror' model for the plasma fluctuations, estimates of an effective radial width, σ, and poloidal correlation length, L p , can be derived from the reflection coefficients. STOR-M results typically give a σ of a few millimetres and an L p of a couple of centimetres. (author)

  4. Statistical fluctuations in cooperative cyclotron radiation

    Science.gov (United States)

    Anishchenko, S. V.; Baryshevsky, V. G.

    2018-01-01

    Shot noise is the cause of statistical fluctuations in cooperative cyclotron radiation generated by an ensemble of electrons oscillating in magnetic field. Autophasing time - the time required for the cooperative cyclotron radiation power to peak - is the critical parameter characterizing the dynamics of electron-oscillators interacting via the radiation field. It is shown that premodulation of charged particles leads to a considerable narrowing of the autophasing time distribution function for which the analytic expression is obtained. When the number of particles Ne exceeds a certain value that depends on the degree to which the particles have been premodulated, the relative root-mean-square deviation (RMSD) of the autophasing time δT changes from a logarithmic dependence on Ne (δT ∼ 1 / lnNe) to square-root (δT ∼ 1 /√{Ne }). A slight energy spread (∼4%) results in a twofold drop of the maximum attainable power of cooperative cyclotron radiation.

  5. Gravitational radiation resistance, radiation damping and field fluctuations

    International Nuclear Information System (INIS)

    Schaefer, G.

    1981-01-01

    Application is made of two different generalised fluctuation-dissipation theorems and their derivations to the calculation of the gravitational quadrupole radiation resistance using the radiation-reaction force given by Misner, Thorne and Wheeler (Gravitation (San Francisco: Freeman) ch 36,37 (1973)) and the usual tidal force on one hand and the tidal force and the free gravitational radiation field on the other hand. The quantum-mechanical version (including thermal generalisations) of the well known classical quadrupole radiation damping formula is obtained as a function of the radiation resistance. (author)

  6. Polarized Radiative Transfer in Fluctuating Stochastic Media

    International Nuclear Information System (INIS)

    Sallah, M.; Degheidy, A.R.; Selim, M.M.

    2009-01-01

    The problem of polarized radiative transfer in a planar cluttered atmospheric medium (like cloudy atmosphere) is proposed. The solution is presented for an arbitrary absorption and scattering cross sections. The extinction function of the medium is assumed to be a continuous random function of position, with fluctuations about the mean taken as Gaussian distributed. The joint probability distribution function of these Gaussian random variables is used to calculate the ensemble-averaged quantities, such as reflectivity, radiative energy and radiative flux, for an arbitrary correlation function. A modified Gaussian probability distribution function is also used to average the solution in order to exclude the probable negative values of the optical variable. The problem is considered in half space medium which has specular reflecting boundary exposed to unit external incident flux. Numerical results of the average reflectivity, average radiant energy and average net flux are obtained for both Gaussian and modified Gaussian probability density functions at different degrees of polarization

  7. Radiation measurement practice for understanding statistical fluctuation of radiation count using natural radiation sources

    International Nuclear Information System (INIS)

    Kawano, Takao

    2014-01-01

    It is known that radiation is detected at random and the radiation counts fluctuate statistically. In the present study, a radiation measurement experiment was performed to understand the randomness and statistical fluctuation of radiation counts. In the measurement, three natural radiation sources were used. The sources were fabricated from potassium chloride chemicals, chemical fertilizers and kelps. These materials contain naturally occurring potassium-40 that is a radionuclide. From high schools, junior high schools and elementary schools, nine teachers participated to the radiation measurement experiment. Each participant measured the 1-min integration counts of radiation five times using GM survey meters, and 45 sets of data were obtained for the respective natural radiation sources. It was found that the frequency of occurrence of radiation counts was distributed according to a Gaussian distribution curve, although the obtained 45 data sets of radiation counts superficially looked to be fluctuating meaninglessly. (author)

  8. Polarization effects in coherent and incoherent photon scattering: survey of measurements and theory relevant to radiation transport calculations

    International Nuclear Information System (INIS)

    Hubbell, J.H.

    1993-01-01

    This report reviews available information on polarization effects arising when photons in the X-ray and gamma-ray energy regime undergo coherent (Rayleigh) scattering and incoherent (Compton) scattering by atomic electrons. In addition to descriptions and discussions of these effects, including estimates of their magnitudes as they apply to radiation transport calculations, an annotated bibliography of 102 selected works covering the period 1905-1991 is provided, with particularly relevant works for the purpose of this report flagged with asterisks (*). A major resource for this report is a 1948 unpublished informal report by L.V. Spencer which has been quoted here almost in its entirety, since, of all the works cited in the annotated bibliography, it appears to be the only one which explicitly and directly addresses the purpose of this report. Hence this valuable material should be re-introduced into the available and current literature. (author). 119 refs., 7 figs

  9. Fluctuation characteristics of solar radiation in crop cultivation

    International Nuclear Information System (INIS)

    Hayashi, S.; Suzuki, H.

    1996-01-01

    The objective of this study was to clarify the fluctuation of solar radiation for long and short periods, which is very crucial for plant growth. Data obtained from a meteorological observatory were used to investigate solar radiation and sunshine duration for a long period. For a short period, observation of global solar radiation and sky solar radiation were conducted in a glass house and at an open field. (1) Yearly average percentage of solar radiation at Kagawa from 1973 to 1994 was 44.3%, and its coefficient of variation was 3.9%. The percentage of possible sunshine and the coefficient were larger than those of solar radiation, 47.3% and 56% respectively. (2) Percentage of possible solar radiation and percentage of possible sunshine showed seasonal variation. Those coefficients of variation both increased exponentially with cloud amount. (3) Variations of global solar radiation and direct solar radiation were more remarkable in the glass house than those in the open field, while variations of sky solar radiation were small in the house and at the open field. (4) The fluctuation of solar radiation observed every 5 minutes was presented as the difference of radiation, present value minus the preceding value. The difference was positive in the morning, negative in the afternoon at the open field. In the house both positive and negative values were obtained the whole day. (5) Diurnal variation of ratio of direct solar radiation to sky solar radiation showed a parabolic effect, whereas it had irregular and large fluctuations at the open field

  10. Comment on 'Hawking radiation from fluctuating black holes'

    NARCIS (Netherlands)

    Khavkine, I.

    2010-01-01

    Takahashi and Soda (2010 Class. Quantum Grav. 27 175008) have recently considered the effect (at lowest non-trivial order) of dynamical, quantized gravitational fluctuations on the spectrum of scalar Hawking radiation from a collapsing Schwarzschild black hole. However, due to an unfortunate choice

  11. Electron beam bunch length characterizations using incoherent and coherent transition radiation on the APS SASE FEL project

    CERN Document Server

    Lumpkin, Alex H; Berg, W J; Lewellen, J W; Sereno, N S; Happek, U

    2000-01-01

    The Advanced Photon Source (APS) injector linac has been reconfigured with a low-emittance RF thermionic gun and a photocathode (PC) RF gun to support self-amplified spontaneous emission (SASE) free-electron laser (FEL) experiments. One of the most critical parameters for optimizing SASE performance (gain length) is the electron beam peak current, which requires a charge measurement and a bunch length measurement capability. We report here initial measurements of the latter using both incoherent optical transition radiation (OTR) and coherent transition radiation (CTR). A visible light Hamamatsu C5680 synchroscan streak camera was used to measure the thermionic RF gun beam's bunch length (sigma approx 2-3 ps) via OTR generated by the beam at 220 MeV and 200 mA macropulse average current. In addition, a CTR monitor (Michelson Interferometer) based on a Golay cell as the far-infrared (FIR) detector has been installed at the 40-MeV station in the beamline. Initial observations of CTR signal strength variation wi...

  12. Fluctuation theory for radiative transfer in random media

    International Nuclear Information System (INIS)

    Bal, Guillaume; Jing Wenjia

    2011-01-01

    We consider the effect of small scale random fluctuations of the constitutive coefficients on boundary measurements of solutions to radiative transfer equations. As the correlation length of the random oscillations tends to zero, the transport solution is well approximated by a deterministic, averaged, solution. In this paper, we analyze the random fluctuations to the averaged solution, which may be interpreted as a central limit correction to homogenization. With the inverse transport problem in mind, we characterize the random structure of the singular components of the transport measurement operator. In regimes of moderate scattering, such components provide stable reconstructions of the constitutive parameters in the transport equation. We show that the random fluctuations strongly depend on the decorrelation properties of the random medium.

  13. Assessing hepatic fibrosis: comparing the intravoxel incoherent motion in MRI with acoustic radiation force impulse imaging in US

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chih-Horng; Liang, Po-Chin; Shih, Tiffany Ting-Fang [National Taiwan University Hospital, Department of Medical Imaging, Taipei (China); National Taiwan University College of Medicine, Department of Radiology, Taipei (China); Ho, Ming-Chih; Hu, Rey-Heng; Lai, Hong-Shiee [National Taiwan University Hospital and College of Medicine, Department of Surgery, Taipei (China); Jeng, Yung-Ming [National Taiwan University Hospital and College of Medicine, Department of Pathology, Taipei (China)

    2015-12-15

    This study compared the diagnostic performance of intravoxel incoherent motion (IVIM) in magnetic resonance imaging (MRI) and acoustic radiation force impulse imaging (ARFI) in ultrasound (US) for liver fibrosis (LF) evaluation. A total of 49 patients scheduled for liver surgery were recruited. LF in the non-tumorous liver parenchyma at the right lobe was estimated using a slow diffusion coefficient, fast diffusion coefficient (D{sub fast}), perfusion fraction (f) of the IVIM parameters, the total apparent diffusion coefficient of conventional diffusion-weighted imaging and the shear wave velocity (Vs) of ARFI. LF was graded using the Metavir scoring system on histological examination. The Spearman rank correlation coefficient for correlation and analysis of variance was used for determining difference. The diagnostic performance was compared using receiver operating characteristic curve analysis. LF exhibited significant correlation with the three parameters D{sub fast}, f, and Vs (r = -0.528, -0.337, and 0.481, respectively, P < 0.05). The D{sub fast} values in the F4 group were significantly lower than those in the F0, F1 and F2 groups. D{sub fast} exhibited a non-inferior performance for diagnosing all fibrosis grades compared with that of Vs. Both IVIM and ARFI provide reliable estimations for the noninvasive assessment of LF. (orig.)

  14. Radiation Belt Transport Driven by Solar Wind Dynamic Pressure Fluctuations

    Science.gov (United States)

    Kress, B. T.; Hudson, M. K.; Ukhorskiy, A. Y.; Mueller, H.

    2012-12-01

    The creation of the Earth's outer zone radiation belts is attributed to earthward transport and adiabatic acceleration of electrons by drift-resonant interactions with electromagnetic fluctuations in the magnetosphere. Three types of radial transport driven by solar wind dynamic pressure fluctuations that have been identified are: (1) radial diffusion [Falthammer, 1965], (2) significant changes in the phase space density radial profile due to a single or few ULF drift-resonant interactions [Ukhorskiy et al., 2006; Degeling et al., 2008], and (3) shock associated injections of radiation belt electrons occurring in less than a drift period [Li et al., 1993]. A progress report will be given on work to fully characterize different forms of radial transport and their effect on the Earth's radiation belts. The work is being carried out by computing test-particle trajectories in electric and magnetic fields from a simple analytic ULF field model and from global MHD simulations of the magnetosphere. Degeling, A. W., L. G. Ozeke, R. Rankin, I. R. Mann, and K. Kabin (2008), Drift resonant generation of peaked relativistic electron distributions by Pc 5 ULF waves, textit{J. Geophys. Res., 113}, A02208, doi:10.1029/2007JA012411. Fälthammar, C.-G. (1965), Effects of Time-Dependent Electric Fields on Geomagnetically Trapped Radiation, J. Geophys. Res., 70(11), 2503-2516, doi:10.1029/JZ070i011p02503. Li, X., I. Roth, M. Temerin, J. R. Wygant, M. K. Hudson, and J. B. Blake (1993), Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC, textit{Geophys. Res. Lett., 20}(22), 2423-2426, doi:10.1029/93GL02701. Ukhorskiy, A. Y., B. J. Anderson, K. Takahashi, and N. A. Tsyganenko (2006), Impact of ULF oscillations in solar wind dynamic pressure on the outer radiation belt electrons, textit{Geophys. Res. Lett., 33}(6), L06111, doi:10.1029/2005GL024380.

  15. Fluctuations of radiative heat exchange between two bodies

    Science.gov (United States)

    Biehs, S.-A.; Ben-Abdallah, P.

    2018-05-01

    We present a theory to describe the fluctuations of nonequilibrium radiative heat transfer between two bodies both in the far- and near-field regimes. As predicted by the blackbody theory, in the far field, we show that the variance of radiative heat flux is of the same order of magnitude as its mean value. However, in the near-field regime, we demonstrate that the presence of surface polaritons makes this variance more than one order of magnitude larger than the mean flux. We further show that the correlation time of heat flux in this regime is comparable to the relaxation time of heat carriers in each medium. This theory could open the way to an experimental investigation of heat exchanges far from the thermal equilibrium condition.

  16. Protein dynamics and stability: The distribution of atomic fluctuations in thermophilic and mesophilic dihydrofolate reductase derived using elastic incoherent neutron scattering

    International Nuclear Information System (INIS)

    Meinhold, Lars; Clement, David; Tehei, M.; Daniel, R.M.; Finney, J.L.; Smith, Jeremy C.

    2008-01-01

    The temperature dependence of the dynamics of mesophilic and thermophilic dihydrofolate reductase is examined using elastic incoherent neutron scattering. It is demonstrated that the distribution of atomic displacement amplitudes can be derived from the elastic scattering data by assuming a (Weibull) functional form that resembles distributions seen in molecular dynamics simulations. The thermophilic enzyme has a significantly broader distribution than its mesophilic counterpart. Furthermore, although the rate of increase with temperature of the atomic mean-square displacements extracted from the dynamic structure factor is found to be comparable for both enzymes, the amplitudes are found to be slightly larger for the thermophilic enzyme. Therefore, these results imply that the thermophilic enzyme is the more flexible of the two

  17. Modeling Incoherent Electron Cloud Effects

    International Nuclear Information System (INIS)

    Vay, Jean-Luc; Benedetto, E.; Fischer, W.; Franchetti, G.; Ohmi, K.; Schulte, D.; Sonnad, K.; Tomas, R.; Vay, J.-L.; Zimmermann, F.; Rumolo, G.; Pivi, M.; Raubenheimer, T.

    2007-01-01

    Incoherent electron effects could seriously limit the beam lifetime in proton or ion storage rings, such as LHC, SPS, or RHIC, or blow up the vertical emittance of positron beams, e.g., at the B factories or in linear-collider damping rings. Different approaches to modeling these effects each have their own merits and drawbacks. We describe several simulation codes which simplify the descriptions of the beam-electron interaction and of the accelerator structure in various different ways, and present results for a toy model of the SPS. In addition, we present evidence that for positron beams the interplay of incoherent electron-cloud effects and synchrotron radiation can lead to a significant increase in vertical equilibrium emittance. The magnitude of a few incoherent e+e- scattering processes is also estimated. Options for future code development are reviewed

  18. Development of procedures for spectrometer brand Spectral Products to capture spectra of incoherent optical radiation for the Laboratorio de Fotonica y Tecnologia Laser Aplicada

    International Nuclear Information System (INIS)

    Arias Avendano, Fabio Andres

    2008-01-01

    The procedure to capture spectra of incoherent optical radiation for the Laboratorio de Fotonica y Tecnologia Laser Aplicada (LAFTLA), of the Escuela de Ingenieria Electrica de la Universidad de Costa Rica is developed through the use of a spectrometer brand Spectral Products. The thorough understanding of manuals spectrometer brand Spectral Products was necessary for the satisfactory development of the project. Spectrometer and the card National Instruments are installed and run both devices with a montage of suitable laboratory. Two catches of spectrum for two different sources of optical radiation are performanced, since damages to the files .ddl precluded that the SM 240 spectrometer worked properly to take more catches to other sources of optical radiation. A final report containing the two catches is produced with the respective analysis. (author) [es

  19. Influence of thermal fluctuations on Cherenkov radiation from fluxons in dissipative Josephson systems

    DEFF Research Database (Denmark)

    Antonov, A. A.; Pankratov, A. L.; Yulin, A. V.

    2000-01-01

    The nonlinear dynamics of fluxons in Josephson systems with dispersion and thermal fluctuations is analyzed using the "quasiparticle" approach to investigate the influence of noise on the Cherenkov radiation effect. Analytical expressions for the stationary amplitude of the emitted radiation...

  20. Volume cross section of auroral radar backscatter and RMS plasma fluctuations inferred from coherent and incoherent scatter data: a response on backscatter volume parameters

    Directory of Open Access Journals (Sweden)

    M. V. Uspensky

    2011-06-01

    Full Text Available Norway and Finland STARE radar measurements in the eastward auroral electrojet are combined with EISCAT CP-1 measurements of the electron density and electric field vector in the common scattering volume to investigate the variation of the auroral radar volume cross section (VCS with the flow angle of observations (radar look direction with respect to the E×B electron drift. The data set available consists of ~6000 points for flow angles of 40–85° and electron drifts between 500 and 2000 m s−1. The EISCAT electron density N(h-profile data are used to estimate the effective electron density, aspect angle and thickness of the backscattering layer. It is shown that the flow angle variation of the VCS is rather weak, only ~5 dB within the range of the considered flow angles. The VCS values themselves respond almost linearly to the square of both the electron drift velocity magnitude and the effective electron density. By adopting the inferred shape of the VCS variation with the flow angle and the VCS dependence upon wavelength, the relative amplitude of electrostatic electron density fluctuations over all scales is estimated. Inferred values of 2–4 percent react nearly linearly to the electron drift velocity in the range of 500–1000 m s−1 but the rate of increase slows down at electron drifts >1000 m s−1 and density fluctuations of ~5.5 percent due to, perhaps, progressively growing nonlinear wave losses.

  1. Small-scale fluctuations in the microwave background radiation and multiple gravitational lensing

    International Nuclear Information System (INIS)

    Kashlinsky, A.

    1988-01-01

    It is shown that multiple gravitational lensing of the microwave background radiation (MBR) by static compact objects significantly attenuates small-scale fluctuations in the MBR. Gravitational lensing, by altering trajectories of MBR photons reaching an observer, leads to (phase) mixing of photons from regions with different initial fluctuations. As a result of this diffusion process the original fluctuations are damped on scales up to several arcmin. An equation that describes this process and its general solution are given. It is concluded that the present upper limits on the amplitude of the MBR fluctuations on small scales cannot constrain theories of galaxy formation. 25 references

  2. Elucidation of the fluctuation history of cosmic radiation and global environmental using AMS

    International Nuclear Information System (INIS)

    Horiuchi, Kazuho

    2008-01-01

    Recently, accuracy of AMS has further been raised in trace amounts of sample. Besides application of 14 C to the age estimation, it has been able to restore in detail the past fluctuation of cosmic radiation strength using the other radioactive isotopes ( 10 Be, 36 Cl etc) in environmental samples and to elucidate the correlation of this with the fluctuation of climate and environment. In this report, the attempts to elucidate the fluctuation history of cosmic radiation and global environment with ice cores using AMS are presented. (M.H.)

  3. Lithium line radiation in turbulent edge plasmas: Effects of low and high frequency temperature fluctuations

    Science.gov (United States)

    Rosato, J.; Capes, H.; Catoire, F.; Kadomtsev, M. B.; Levashova, M. G.; Lisitsa, V. S.; Marandet, Y.; Rosmej, F. B.; Stamm, R.

    2011-08-01

    In lithium-wall-conditioned tokamaks, the line radiation due to the intrinsic impurities (Li/Li+/Li++) plays a significant role on the power balance. Calculations of the radiation losses are usually performed using a stationary collisional-radiative model, assuming constant values for the plasma parameters (Ne, Te,…). Such an approach is not suitable for turbulent plasmas where the various parameters are time-dependent. This is critical especially for the edge region, where the fluctuation rates can reach several tens of percents [e.g. J.A. Boedo, J. Nucl. Mater. 390-391 (2009) 29-37]. In this work, the role of turbulence on the radiated power is investigated with a statistical formalism. A special emphasis is devoted to the role of temperature fluctuations, successively for low-frequency fluctuations and in the general case where the characteristic turbulence frequencies can be comparable to the collisional and radiative rates.

  4. Dynamics of voids and clusters and fluctuations in the cosmic background radiation

    International Nuclear Information System (INIS)

    Salpeter, E.E.

    1983-01-01

    The author summarizes briefly calculations on spherically symmetric models without dissipation for the dynamical development of large voids and galaxy (super)clusters from small underdensities and overdensities, respectively, at the recombination era. Implications are mentioned and conjectures for more complex geometries are discussed. He infers the density fluctuations which must have been present just after the recombination era to produce some present-day configuration. Fluctuations in the present-day cosmic background radiation are related to this and their inferred amplitude depends very strongly on the present-day value of the cosmological density parameter. The relation to observed upper limits on these fluctuations are discussed. (Auth.)

  5. Ocean acidification alters the photosynthetic responses of a coccolithophorid to fluctuating ultraviolet and visible radiation.

    Science.gov (United States)

    Jin, Peng; Gao, Kunshan; Villafañe, Virginia E; Campbell, Douglas A; Helbling, E Walter

    2013-08-01

    Mixing of seawater subjects phytoplankton to fluctuations in photosynthetically active radiation (400-700 nm) and ultraviolet radiation (UVR; 280-400 nm). These irradiance fluctuations are now superimposed upon ocean acidification and thinning of the upper mixing layer through stratification, which alters mixing regimes. Therefore, we examined the photosynthetic carbon fixation and photochemical performance of a coccolithophore, Gephyrocapsa oceanica, grown under high, future (1,000 μatm) and low, current (390 μatm) CO₂ levels, under regimes of fluctuating irradiances with or without UVR. Under both CO₂ levels, fluctuating irradiances, as compared with constant irradiance, led to lower nonphotochemical quenching and less UVR-induced inhibition of carbon fixation and photosystem II electron transport. The cells grown under high CO₂ showed a lower photosynthetic carbon fixation rate but lower nonphotochemical quenching and less ultraviolet B (280-315 nm)-induced inhibition. Ultraviolet A (315-400 nm) led to less enhancement of the photosynthetic carbon fixation in the high-CO₂-grown cells under fluctuating irradiance. Our data suggest that ocean acidification and fast mixing or fluctuation of solar radiation will act synergistically to lower carbon fixation by G. oceanica, although ocean acidification may decrease ultraviolet B-related photochemical inhibition.

  6. The influence of non-equilibrium fluctuations on radiation damage and recovery of metals under irradiation

    International Nuclear Information System (INIS)

    Dubinko, V.I.; Klepikov, V.F.

    2007-01-01

    In the conventional theory of radiation damage, it is assumed that the main effect of irradiation is due to formation of Frenkel pairs of vacancies and self-interstitial atoms (SIAs) and their clusters. The difference in absorption of vacancies and SIAs by primary or radiation-induced extended defects (EDs) is thought to be the main reason of microstructural evolution under irradiation. On the other hand, the recovery of radiation damage is thought to be driven exclusively by thermal fluctuations resulting in the vacancy evaporation from voids (void annealing) or dislocations (thermal creep) and in the fluctuation-driven overcoming of obstacles by gliding dislocations (plastic strain). However, these recovery mechanisms can be efficient only at sufficiently high temperatures. At lower irradiation temperatures, the main driving force of the recovery processes may be due to nonequilibrium fluctuations of energy states of the atoms surrounding EDs arising as a result of scattering of radiation-induced excitations of atomic and electronic structure at EDs. In the present paper, the mechanisms of nonequilibrium fluctuations that result in such phenomena as the void shrinkage under irradiation at low temperatures (or high dose rates), irradiation creep and irradiation-induced increase of plasticity under sub-threshold irradiation was considered

  7. New limits to the small scale fluctuations in the cosmic background radiation

    International Nuclear Information System (INIS)

    Kellermann, K.I.; Fomalont, E.B.; Wall, J.V.

    1983-01-01

    The VLA has been used at 4.9 GHz to observe a small region of sky in order to extend the radio source count to low flux density (Fomalont et al., these proceedings) and to look for small scale fluctuations in the 2.7 K cosmic microwave background radiation. (Auth.)

  8. Spectral measurements of fluctuating ω/sub pe/ radiation from Alcator C tokamak

    International Nuclear Information System (INIS)

    Gandy, R.F.; Yates, D.

    1984-01-01

    High resolution spectral measurements have been made of the fluctuating electron plasma frequency (ω/sub pe/) radiation from Alcator C. Three techniques have been used in making the measurements. Features as narrow as 350 kHz have been observed (Δf/f approx. = 6 x 10 -6 ), impling that a highly coherent process is responsible for the emission

  9. Lithium line radiation in turbulent edge plasmas: Effects of low and high frequency temperature fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Rosato, J., E-mail: joel.rosato@univ-provence.fr [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France); Capes, H.; Catoire, F. [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France); Kadomtsev, M.B.; Levashova, M.G.; Lisitsa, V.S. [ITP, Russian Research Center ' Kurchatov Institute' , Moscow (Russian Federation); Marandet, Y. [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France); Rosmej, F.B. [LULI, UMR 7605, Universite Pierre et Marie Curie/CNRS, 4 Place Jussieu, Case 128, F-75252 Paris Cedex 05 (France); Stamm, R. [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France)

    2011-08-01

    In lithium-wall-conditioned tokamaks, the line radiation due to the intrinsic impurities (Li/Li{sup +}/Li{sup ++}) plays a significant role on the power balance. Calculations of the radiation losses are usually performed using a stationary collisional-radiative model, assuming constant values for the plasma parameters (N{sub e}, T{sub e},...). Such an approach is not suitable for turbulent plasmas where the various parameters are time-dependent. This is critical especially for the edge region, where the fluctuation rates can reach several tens of percents [e.g. J.A. Boedo, J. Nucl. Mater. 390-391 (2009) 29-37]. In this work, the role of turbulence on the radiated power is investigated with a statistical formalism. A special emphasis is devoted to the role of temperature fluctuations, successively for low-frequency fluctuations and in the general case where the characteristic turbulence frequencies can be comparable to the collisional and radiative rates.

  10. Incoherences of Brazilian labour laws face to present radioprotection concepts

    International Nuclear Information System (INIS)

    Borges, J.C.

    1996-01-01

    The Brazilian labour legislation establishes, since 1950, some privileges for people working in activities which imply exposure to ionizing radiations. Comparing the present legal framework with technical radioprotection knowledge, one can detect several incoherences covering: classification of such activities; additional payments; reduced labour journey; more vacations; medical surveillance; early retirements; special norms for women. An analysis of these incoherences lead us to propose a new frame of labour rights and radioprotection norms, coupling Brazilian juridical principles and modern radioprotection knowledge. (author)

  11. Estimating radiative feedbacks from stochastic fluctuations in surface temperature and energy imbalance

    Science.gov (United States)

    Proistosescu, C.; Donohoe, A.; Armour, K.; Roe, G.; Stuecker, M. F.; Bitz, C. M.

    2017-12-01

    Joint observations of global surface temperature and energy imbalance provide for a unique opportunity to empirically constrain radiative feedbacks. However, the satellite record of Earth's radiative imbalance is relatively short and dominated by stochastic fluctuations. Estimates of radiative feedbacks obtained by regressing energy imbalance against surface temperature depend strongly on sampling choices and on assumptions about whether the stochastic fluctuations are primarily forced by atmospheric or oceanic variability (e.g. Murphy and Forster 2010, Dessler 2011, Spencer and Braswell 2011, Forster 2016). We develop a framework around a stochastic energy balance model that allows us to parse the different contributions of atmospheric and oceanic forcing based on their differing impacts on the covariance structure - or lagged regression - of temperature and radiative imbalance. We validate the framework in a hierarchy of general circulation models: the impact of atmospheric forcing is examined in unforced control simulations of fixed sea-surface temperature and slab ocean model versions; the impact of oceanic forcing is examined in coupled simulations with prescribed ENSO variability. With the impact of atmospheric and oceanic forcing constrained, we are able to predict the relationship between temperature and radiative imbalance in a fully coupled control simulation, finding that both forcing sources are needed to explain the structure of the lagged-regression. We further model the dependence of feedback estimates on sampling interval by considering the effects of a finite equilibration time for the atmosphere, and issues of smoothing and aliasing. Finally, we develop a method to fit the stochastic model to the short timeseries of temperature and radiative imbalance by performing a Bayesian inference based on a modified version of the spectral Whittle likelihood. We are thus able to place realistic joint uncertainty estimates on both stochastic forcing and

  12. Transverse resonance-radiation pressure on atomic beams and the influence of fluctuations

    International Nuclear Information System (INIS)

    Bjorkholm, J.E.; Freeman, R.R.; Ashkin, A.; Pearson, D.B.

    1979-01-01

    We have experimentally demonstrated that a beam of neutral sodium atoms can be focused to a spot diameter of approx. 50 μ using the transverse dipole resonance-radiation pressure exerted by a 40 mW laser beam. Simple analysis shows that in some cases the spot sizes are limited by the random fluctuations of the spontaneous radiation pressure; with 1 W of laser power, spot sizes less than 10 μ should be attainable. The effects of heating by spontaneous scattering can have important detrimental effects in other applications of resonance - radiation pressure on atoms, such as the slowing or guiding of atoms. Consideration of heating effects is of paramount importance in the design of optical traps for neutral atoms. (KBE)

  13. Non-classical radiation transport in random media with fluctuating densities

    International Nuclear Information System (INIS)

    Dyuldya, S.V.; Bratchenko, M.I.

    2012-01-01

    The ensemble averaged propagation kernels of the non-classical radiation transport are studied by means of the proposed application of the stochastic differential equation random medium generators. It is shown that the non-classical transport is favored in long-correlated weakly fluctuating media. The developed kernel models have been implemented in GEANT4 and validated against the d ouble Monte Carlo m odeling of absorptions curves of disperse neutron absorbers and γ-albedos from a scatterer/absorber random mix

  14. Subphotospheric fluctuations in magnetized radiative envelopes: contribution from unstable magnetosonic waves

    Science.gov (United States)

    Sen, Koushik; Fernández, Rodrigo; Socrates, Aristotle

    2018-06-01

    We examine the excitation of unstable magnetosonic waves in the radiative envelopes of intermediate- and high-mass stars with a magnetic field of ˜kG strength. Wind clumping close to the star and microturbulence can often be accounted for when including small-scale, subphotospheric density or velocity perturbations. Compressional waves - with wavelengths comparable to or shorter than the gas pressure scale height - can be destabilized by the radiative flux in optically thick media when a magnetic field is present, in a process called the radiation-driven magneto-acoustic instability (RMI). The instability does not require radiation or magnetic pressure to dominate over gas pressure, and acts independently of subsurface convection zones. Here we evaluate the conditions for the RMI to operate on a grid of stellar models covering a mass range 3-40 M⊙ at solar metallicity. For a uniform 1 kG magnetic field, fast magnetosonic modes are unstable down to an optical depth of a few tens, while unstable slow modes extend beyond the depth of the iron convection zone. The qualitative behaviour is robust to magnetic field strength variations by a factor of a few. When combining our findings with previous results for the saturation amplitude of the RMI, we predict velocity fluctuations in the range ˜0.1-10 km s-1. These amplitudes are a monotonically increasing function of the ratio of radiation to gas pressure, or alternatively, of the zero-age main sequence mass.

  15. UVR-induced photosynthetic inhibition dominates over DNA damage in marine dinoflagellates exposed to fluctuating solar radiation regimes

    NARCIS (Netherlands)

    Helbling, E. Walter; Buma, Anita G. J.; van de Poll, Willem; Fernandez Zenoff, M. Veronica; Villafane, Virginia E.

    2008-01-01

    The combined effect of solar radiation (UV-B (280-315 nm), UWA (315-400 nm) and PAR (400-700 nm)) and vertical mixing (i.e., fluctuating radiation regimes) on the marine dinoflagellates Gymnodinium chlorophorum, Heterocapsa triquetra and Prorocentrum micans was investigated during the austral spring

  16. Full counting statistics of multiple Andreev reflections in incoherent diffusive superconducting junctions

    International Nuclear Information System (INIS)

    Samuelsson, P.

    2007-01-01

    We present a theory for the full distribution of current fluctuations in incoherent diffusive superconducting junctions, subjected to a voltage bias. This theory of full counting statistics of incoherent multiple Andreev reflections is valid for an arbitrary applied voltage. We present a detailed discussion of the properties of the first four cumulants as well as the low and high voltage regimes of the full counting statistics. (orig.)

  17. Coherence Inherent in an Incoherent Synchrotron Radio Source ...

    Indian Academy of Sciences (India)

    It is well known that synchrotron radiation mechanism does not allow MASER type coherent emission (Pacholczyk 1970). Here we show that coherence can naturally occur in a synchrotron ... cally thick region (Fig. 1), then divides the synchrotron spectrum into an incoherent. 1A thin flat circular unleavened Indian bread.

  18. Acoustic Holography With Incoherent Sources

    NARCIS (Netherlands)

    Druyvesteyn, W.F.; Raangs, R.

    2005-01-01

    In near field acoustic holography the sound field is scanned near the surface of the vibrating object; from these measurements the vibration of the structure can be calculated. In the case of correlated sources one reference signal is sufficient. When incoherent sources are present the separation of

  19. Effect of quantum fluctuations of synchrotron radiation on the dynamics of particles in high-energy microtrons

    International Nuclear Information System (INIS)

    Bessonov, E.G.

    1987-01-01

    Crosbie has demonstrated numerically that the effect of quantum fluctuation of synchrotron radiation on the beam emittance becomes significant in microtrons for an energy of more than 1 GeV. In this paper the authors give analytic expressions that describe this phenomenon and analyze these expressions

  20. Radiation propagation in random media: From positive to negative correlations in high-frequency fluctuations

    International Nuclear Information System (INIS)

    Davis, Anthony B.; Mineev-Weinstein, Mark B.

    2011-01-01

    We survey research on radiation propagation or ballistic particle motion through media with randomly variable material density, and we investigate the topic with an emphasis on very high spatial frequencies. Our new results are based on a specific variability model consisting of a zero-mean Gaussian scaling noise riding on a constant value that is large enough with respect to the amplitude of the noise to yield overwhelmingly non-negative density. We first generalize known results about sub-exponential transmission from regular functions, which are almost everywhere continuous, to merely 'measurable' ones, which are almost everywhere discontinuous (akin to statistically stationary noises), with positively correlated fluctuations. We then use the generalized measure-theoretic formulation to address negatively correlated stochastic media without leaving the framework of conventional (continuum-limit) transport theory. We thus resolve a controversy about recent claims that only discrete-point process approaches can accommodate negative correlations, i.e., anti-clustering of the material particles. We obtain in this case the predicted super-exponential behavior, but it is rather weak. Physically, and much like the alternative discrete-point process approach, the new model applies most naturally to scales commensurate with the inter-particle distance in the material, i.e., when the notion of particle density breaks down due to Poissonian-or maybe not-so-Poissonian-number-count fluctuations occur in the sample volume. At the same time, the noisy structure must prevail up to scales commensurate with the mean-free-path to be of practical significance. Possible applications are discussed.

  1. Fluctuations in induced charge introduced by Te inclusions within CdZnTe radiation detectors

    International Nuclear Information System (INIS)

    Bale, Derek S.

    2010-01-01

    Recently, homogenization theory based on a multiple-scale perturbation of the electron transport equation has been used to derive a mathematical framework for modeling the excess charge lost to Te inclusions within radiation detectors based on semi-insulating cadmium zinc telluride (CdZnTe). In that theory, the heterogeneous material is mathematically replaced by a homogenized CdZnTe crystal whose effective electron attenuation length incorporates the additional uniform electron trapping caused by the inclusions. In this paper, the homogenization theory is extended to incorporate fluctuations in the induced charge (i.e., charge collection nonuniformities) introduced by the random position and size distributions of a noncorrelated population of small (i.e, <20 μm) Te inclusions. Analysis of the effective parameters derived within the homogenized framework is used to develop a probability distribution of effective electron attenuation lengths, and therefore effective mobility-lifetime products, as a function of both the position and size distribution of Te inclusions. Example distributions are detailed for the case of an exponential size distribution at various number densities. Further, it is demonstrated that the inclusion-induced material nonuniformities derived in this paper can be numerically sampled efficiently, making them applicable to Monte Carlo device simulation of realistic CdZnTe detectors. Simulated charge induction maps and pulse-height spectra are presented and compared to recently published measurements.

  2. Study of the fluctuations of the partial and total radiative widths by neutron capture resonance method; Etude des fluctuations des largeurs radiatives partielles et totales par la capture des neutrons de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, V D [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-06-01

    Radiative capture experiments by neutron time-of-flight methods have been made for following studies: distribution of partial radiative widths, effects of correlation between different radiative transitions, fluctuations of total radiative widths {gamma}{sub {gamma}} from resonance to resonance, variation of {gamma}{sub {gamma}} with number of mass and the search for the existence of potential capture. Also, some other experiments with the use of neutron capture gamma-rays spectra have been investigated. (author) [French] Par la capture des neutrons de resonance dont les energies sont selectionnees a l'aide de la technique du temps de vol, differents types d'experiences ont ete realisees concernant les etudes des distributions des largeurs radiatives partielles, des effets de correlation entre differentes voies de desexcitation, de la fluctuation des largeurs radiatives totales {gamma}{sub {gamma}} de resonance a resonance, de la variation de la quantite {gamma}{sub {gamma}} en fonction du nombre de masse et de la mise en evidence de l'existence du processus de capture potentielle. Quelques autres applications de l'emploi du spectre de rayons gamma ont egalement ete presentees. (auteur)

  3. Study of the fluctuations of the partial and total radiative widths by neutron capture resonance method; Etude des fluctuations des largeurs radiatives partielles et totales par la capture des neutrons de resonance

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, V.D. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-06-01

    Radiative capture experiments by neutron time-of-flight methods have been made for following studies: distribution of partial radiative widths, effects of correlation between different radiative transitions, fluctuations of total radiative widths {gamma}{sub {gamma}} from resonance to resonance, variation of {gamma}{sub {gamma}} with number of mass and the search for the existence of potential capture. Also, some other experiments with the use of neutron capture gamma-rays spectra have been investigated. (author) [French] Par la capture des neutrons de resonance dont les energies sont selectionnees a l'aide de la technique du temps de vol, differents types d'experiences ont ete realisees concernant les etudes des distributions des largeurs radiatives partielles, des effets de correlation entre differentes voies de desexcitation, de la fluctuation des largeurs radiatives totales {gamma}{sub {gamma}} de resonance a resonance, de la variation de la quantite {gamma}{sub {gamma}} en fonction du nombre de masse et de la mise en evidence de l'existence du processus de capture potentielle. Quelques autres applications de l'emploi du spectre de rayons gamma ont egalement ete presentees. (auteur)

  4. A stochastic simulation model for reliable PV system sizing providing for solar radiation fluctuations

    International Nuclear Information System (INIS)

    Kaplani, E.; Kaplanis, S.

    2012-01-01

    Highlights: ► Solar radiation data for European cities follow the Extreme Value or Weibull distribution. ► Simulation model for the sizing of SAPV systems based on energy balance and stochastic analysis. ► Simulation of PV Generator-Loads-Battery Storage System performance for all months. ► Minimum peak power and battery capacity required for reliable SAPV sizing for various European cities. ► Peak power and battery capacity reduced by more than 30% for operation 95% success rate. -- Abstract: The large fluctuations observed in the daily solar radiation profiles affect highly the reliability of the PV system sizing. Increasing the reliability of the PV system requires higher installed peak power (P m ) and larger battery storage capacity (C L ). This leads to increased costs, and makes PV technology less competitive. This research paper presents a new stochastic simulation model for stand-alone PV systems, developed to determine the minimum installed P m and C L for the PV system to be energy independent. The stochastic simulation model developed, makes use of knowledge acquired from an in-depth statistical analysis of the solar radiation data for the site, and simulates the energy delivered, the excess energy burnt, the load profiles and the state of charge of the battery system for the month the sizing is applied, and the PV system performance for the entire year. The simulation model provides the user with values for the autonomy factor d, simulating PV performance in order to determine the minimum P m and C L depending on the requirements of the application, i.e. operation with critical or non-critical loads. The model makes use of NASA’s Surface meteorology and Solar Energy database for the years 1990–2004 for various cities in Europe with a different climate. The results obtained with this new methodology indicate a substantial reduction in installed peak power and battery capacity, both for critical and non-critical operation, when compared to

  5. Fluctuations in radiation backgrounds at high redshift and the first stars

    Science.gov (United States)

    Holzbauer, Lauren Nicole

    The first stars to light up our universe are as yet unseen, but there have been many attempts to elucidate their properties. The characteristics of these stars (`Population/Pop III' stars) that we do know lie mostly within theory; they formed out of metal-free hydrogen and helium gas contained in dark matter minihalos at redshifts z 20-30. The extent to which Pop III star formation reached into later times is unknown. Current and near future instruments are incapable of resolving individual Pop III stars. Consequently, astronomers must devise creative means with which to indirectly predict and measure and their properties. In this thesis, we will investigate a few of those means. We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons (11.5-13.6 eV) are of particular interest because they dissociate molecular hydrogen, the primary coolant in the first minihalos that is necessary for star formation. By using a variation of the `halo model', which describes the spatial distribution and clustering of halos, we can efficiently generate power spectra for these backgrounds. Spatial fluctuations in the LW and (indirectly) the Lyman-alpha BG can tell us about the transition from primordial star formation to a more metal-enriched mode that marks the beginning of the second generation of stars in our Universe. The Near Infrared Background (NIRB) has for some time been considered a potential tool with which to indirectly observe the first stars. Ultraviolet (UV) emission from these stars is redshifted into the NIR band, making the NIRB amenable for hunting Pop III stellar signatures. There have been several measurements of the NIRB and subsequent theoretical studies attempting to explain them in recent years. Though controversial, residual levels of the mean NIRB intensity and anisotropies have been

  6. Scattering of lower-hybrid waves by drift-wave density fluctuations: solutions of the radiative transfer equation

    International Nuclear Information System (INIS)

    Andrews, P.L.; Perkins, F.W.

    1983-01-01

    The investigation of the scattering of lower-hybrid waves by density fluctuations arising from drift waves in tokamaks is distinguished by the presence in the wave equation of a large, random, derivative-coupling term. The propagation of the lower-hybrid waves is well represented by a radiative transfer equation when the scale size of the density fluctuations is small compared to the overall plasma size. The radiative transfer equation is solved in two limits: first, the forward scattering limit, where the scale size of density fluctuations is large compared to the lower-hybrid perpendicular wavelength, and second, the large-angle scattering limit, where this inequality is reversed. The most important features of these solutions are well represented by analytical formulas derived by simple arguments. Based on conventional estimates for density fluctuations arising from drift waves and a parabolic density profile, the optical depth tau for scattering through a significant angle, is given by tauroughly-equal(2/N 2 /sub parallel/) (#betta#/sub p/i0/#betta#) 2 (m/sub e/c 2 /2T/sub i/)/sup 1/2/ [c/α(Ω/sub i/Ω/sub e/)/sup 1/2/ ], where #betta#/sub p/i0 is the central ion plasma frequency and T/sub i/ denotes the ion temperature near the edge of the plasma. Most of the scattering occurs near the surface. The transmission through the scattering region scales as tau - 1 and the emerging intensity has an angular spectrum proportional to cos theta, where sin theta = k/sub perpendicular/xB/sub p//(k/sub perpendicular/B/sub p/), and B/sub p/ is the poloidal field

  7. Compensation for incoherent ground motion

    International Nuclear Information System (INIS)

    Shigeru, Takeda; Hiroshi, Matsumoto; Masakazu, Yoshioka; Yasunori, Takeuchi; Kikuo, Kudo; Tsuneya, Tsubokawa; Mitsuaki, Nozaki; Kiyotomo, Kawagoe

    1999-01-01

    The power spectrum density and coherence function for ground motions are studied for the construction of the next generation electron-positron linear collider. It should provide a center of mass energy between 500 GeV-1 TeV with luminosity as high as 10 33 to 10 34 cm -2 sec -1 . Since the linear collider has a relatively slow repetition rate, large number of particles and small sizes of the beam should be generated and preserved in the machine to obtain the required high luminosity. One of the most critical parameters is the extremely small vertical beam size at the interaction point, thus a proper alignment system for the focusing and accelerating elements of the machine is necessary to achieve the luminosity. We describe recent observed incoherent ground motions and an alignment system to compensate the distortion by the ground motions. (authors)

  8. Coherence and incoherence collective behavior in financial market

    Science.gov (United States)

    Zhao, Shangmei; Xie, Qiuchao; Lu, Qing; Jiang, Xin; Chen, Wei

    2015-10-01

    Financial markets have been extensively studied as highly complex evolving systems. In this paper, we quantify financial price fluctuations through a coupled dynamical system composed of phase oscillators. We find that a Financial Coherence and Incoherence (FCI) coexistence collective behavior emerges as the system evolves into the stable state, in which the stocks split into two groups: one is represented by coherent, phase-locked oscillators, the other is composed of incoherent, drifting oscillators. It is demonstrated that the size of the coherent stock groups fluctuates during the economic periods according to real-world financial instabilities or shocks. Further, we introduce the coherent characteristic matrix to characterize the involvement dynamics of stocks in the coherent groups. Clustering results on the matrix provides a novel manifestation of the correlations among stocks in the economic periods. Our analysis for components of the groups is consistent with the Global Industry Classification Standard (GICS) classification and can also figure out features for newly developed industries. These results can provide potentially implications on characterizing the inner dynamical structure of financial markets and making optimal investment into tragedies.

  9. Development of a LiF-filter for measuring plasma fluctuations in the far ultraviolet radiation spectral range

    International Nuclear Information System (INIS)

    Schittenhelm, M.

    1991-06-01

    The investigations of fluctuations and anomalous transport lie at hart of the tokamak research program, especially in the shear zone close to and beyond the last closed flux surface. Until now fluctuation measurements using plasma radiation were only made on the edge of the plasma, since they rely on the H α emission. In order to measure electron density fluctuations with good spatial and temporal resolution in the shear zone, the OVI doublet (2s-2p) can be observed. These are very strong impurity emission lines in the VUV region (103.2 nm and 103.8 nm) emitted from a narrow layer close to the separatrix. To get an image of this layer and to achieve enough intensity for a good temporal resolution, it is necessary to develop a filter with high transmission. A possible candidate is lithium fluoride (LiF), which transmits light at shorter wavelength than other materials. By cooling LiF crystals from 300 K to 220 K the cutoff wavelength decreases from 105 nm to about 103 nm. This master thesis presents a detailed investigation of the transmission of LiF near the cutoff wavelength. Crystal sheets produced by different manufactures were tested and the temperature dependence of the cutoff edge was investigated. (orig./AH)

  10. Fluctuations in pO2 in poorly and well-oxygenated spontaneous canine tumors before and during fractionated radiation therapy.

    Science.gov (United States)

    Brurberg, Kjetil G; Skogmo, Hege K; Graff, Bjørn A; Olsen, Dag R; Rofstad, Einar K

    2005-11-01

    The spatial heterogeneity in oxygen tension (pO2) in tumor tissue has been studied extensively, whereas, the information about the temporal heterogeneity is sparse. The purpose of the present study was to search for pO2 fluctuations in untreated and irradiated spontaneous canine tumors, and to investigate whether there is a relationship between overall tumor oxygenation status and pO2 fluctuation pattern. Six dogs scheduled for radiation therapy of head and neck cancer were included in the study. The primary tumors were irradiated with 18 fractions of 3 Gy. Eppendorf polarographic electrodes and OxyLite fluorescence probes were used to measure overall oxygenation status and pO2 fluctuation pattern, respectively. Tissue pO2 was recorded at three subsequent days prior to treatment, and immediately before radiation fraction 4, 7, and 10. Overall oxygenation status differed substantially among the tumors. Radiation therapy had no consistent effect on overall oxygenation status. Fluctuations in pO2 were detected in untreated as well as irradiated tumors, and independent of whether the tumors were poorly or well oxygenated. Fluctuations in pO2 can occur in untreated and irradiated spontaneous canine tumors. There is no correlation between pO2 fluctuation pattern and overall tumor oxygenation status.

  11. Vacuum fluctuations and radiation reaction contributions to the resonance dipole-dipole interaction between two atoms near a reflecting boundary

    Science.gov (United States)

    Zhou, Wenting; Rizzuto, Lucia; Passante, Roberto

    2018-04-01

    We investigate the resonance dipole-dipole interaction energy between two identical atoms, one in the ground state and the other in the excited state, interacting with the electromagnetic field in the presence of a perfectly reflecting plane boundary. The atoms are prepared in a correlated (symmetric or antisymmetric) Bell-type state. Following a procedure due to Dalibard et al. [J. Dalibard et al., J. Phys. (Paris) 43, 1617 (1982);, 10.1051/jphys:0198200430110161700 J. Phys. (Paris) 45, 637 (1984), 10.1051/jphys:01984004504063700], we separate the contributions of vacuum fluctuations and radiation reaction (source) field to the resonance interaction energy between the two atoms and show that only the source field contributes to the interatomic interaction, while vacuum field fluctuations do not. By considering specific geometric configurations of the two-atom system with respect to the mirror and specific choices of dipole orientations, we show that the presence of the mirror significantly affects the resonance interaction energy and that different features appear with respect to the case of atoms in free space, for example, a change in the spatial dependence of the interaction. Our findings also suggest that the presence of a boundary can be exploited to tailor and control the resonance interaction between two atoms, as well as the related energy transfer process. The possibility of observing these phenomena is also discussed.

  12. Influence of radiation on intensity of fluctuating asymmetry at Betula pendula

    International Nuclear Information System (INIS)

    Kipen', V.N.; Krapivina, N.S.; Sinevich, E.A.; Baranov, A.S.; Mel'nov, S.B.; Lozinskaya, O.V.

    2008-01-01

    Analysis of anthropogenic pressure was conducted in cities having different industrial development levels and with different levels of radiation contamination. Based on obtained data one could state that environmental effect level in different regions of Belarus varies in wide range caused by unevenness of anthropogenic effect. (authors)

  13. Radiation turbulence interactions in pulverized coal flames: Chaotic map models of soot fluctuations in turbulent diffusion flames. Quarterly report, October 1995--December 1995

    Energy Technology Data Exchange (ETDEWEB)

    McDonough, J.M.; Menguc, M.P.; Mukerji, S.; Swabb, S.; Manickavasagam, S.; Ghosal, S.

    1995-12-31

    In this paper, we introduce a methodology to characterize soot volume fraction fluctuations in turbulent diffusion flames via chaotic maps. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames is deterministic in nature, rather than statistical. Out objective is to develop models to mimic these fluctuations. The models will be used eventually in comprehensive algorithms to study the true physics of turbulent flames and the interaction of turbulence with radiation. To this extent, we measured the time series of soot scattering coefficient in an ethylene diffusion flame from light scattering experiments. Following this, corresponding power spectra and delay maps were calculated. It was shown that if the data were averaged, the characteristics of the fluctuations were almost completely washed out. The psds from experiments were successfully modeled using a series of logistic maps.

  14. Biological growth in bodies with incoherent interfaces

    Science.gov (United States)

    Swain, Digendranath; Gupta, Anurag

    2018-01-01

    A general theory of thermodynamically consistent biomechanical-biochemical growth in a body, considering mass addition in the bulk and at an incoherent interface, is developed. The incoherency arises due to incompatibility of growth and elastic distortion tensors at the interface. The incoherent interface therefore acts as an additional source of internal stress besides allowing for rich growth kinematics. All the biochemicals in the model are essentially represented in terms of nutrient concentration fields, in the bulk and at the interface. A nutrient balance law is postulated which, combined with mechanical balances and kinetic laws, yields an initial-boundary-value problem coupling the evolution of bulk and interfacial growth, on the one hand, and the evolution of growth and nutrient concentration on the other. The problem is solved, and discussed in detail, for two distinct examples: annual ring formation during tree growth and healing of cutaneous wounds in animals.

  15. Non-primordial origin of the cosmic background radiation and pregalactic density fluctuations

    International Nuclear Information System (INIS)

    Froehlich, H.E.; Mueller, V.; Oleak, H.

    1984-01-01

    Assumptions of a tepid Universe and a smaller primordial contribution to the 3 K background are made to show that Pop III stars may be responsible for the 3 K background and cosmic ray entropy. The 3 K background would be caused by thermalized stellar radiation produced by metallized intergalactic dust formed in first generation stars. A range of mass scales and amplification factors of density perturbations in the early Universe is examined below the Jeans mass for gravitational instabilities. The density perturbations that could have been present at small enough mass scales could have survived and generated sonic modes that propagated through the plasma era and, when combined with additional gravitationally unstable entropy disturbances after recombination, triggered the formation of Pop III stars. 13 references

  16. Diversification in a fluctuating island setting: rapid radiation of Ohomopterus ground beetles in the Japanese Islands.

    Science.gov (United States)

    Sota, Teiji; Nagata, Nobuaki

    2008-10-27

    The Japanese Islands have been largely isolated from the East Asian mainland since the Early Pleistocene, allowing the diversification of endemic lineages. Here, we explore speciation rates and historical biogeography of the ground beetles of the subgenus Ohomopterus (genus Carabus) based on nuclear and mitochondrial gene sequences. Ohomopterus diverged into 15 species during the Pleistocene. The speciation rate was 1.92 Ma(-1) and was particularly fast (2.37 Ma(-1)) in a group with highly divergent genitalia. Speciation occurred almost solely within Honshu, the largest island with complex geography. Species diversity is highest in central Honshu, where closely related species occur parapatrically and different-sized species co-occur. Range expansion of some species in the past has resulted in such species assemblages. Introgressive hybridization, at least for mitochondrial DNA, has occurred repeatedly between species in contact, but has not greatly disturbed species distinctness. Small-island populations of some species were separated from main-island populations only after the last glacial (or the last interglacial) period, indicating that island isolation had little role in speciation. Thus, the speciation and formation of the Ohomopterus assemblage occurred despite frequent opportunities for secondary contact and hybridization and the lack of persistent isolation. This radiation was achieved without substantial ecological differentiation, but with marked differentiation in mechanical agents of reproductive isolation (body size and genital morphology).

  17. Incoherent and coherent backscattering of light by a layer of densely packed random medium

    Energy Technology Data Exchange (ETDEWEB)

    Tishkovets, Victor P. [Institute of Radio Astronomy of NASU, 4 Chervonopraporna Street, Kharkiv 61002 (Ukraine)], E-mail: tishkovets@ira.kharkov.ua

    2007-12-15

    The problem of light scattering by a layer of densely packed discrete random medium is considered. The theory of light scattering by systems of nonspherical particles is applied to derive equations corresponding to incoherent (diffuse) and interference parts of radiation reflected from the medium. A solution of the system of linear equations describing light scattering by a system of particles is represented by iteration. It is shown that the symmetry properties of the T-matrices and of the translation coefficients for the vector Helmholtz harmonics lead to the reciprocity relation for an arbitrary iteration. This relation is applied to consider the backscattering enhancement phenomenon. Equations expressing the incoherent and interference parts of reflected light from statistically homogeneous and isotropic plane-parallel layer of medium are given. In the exact backscattering direction the relation between incoherent and interference parts is identical to that of sparse media.

  18. Nucleotide fluctuation of radiation-resistant Halobacterium sp. NRC-1 single-stranded DNA-binding protein (RPA) genes

    Science.gov (United States)

    Holden, Todd; Tremberger, G., Jr.; Cheung, E.; Subramaniam, R.; Gadura, N.; Schneider, P.; Sullivan, R.; Flamholz, A.; Lieberman, D.; Cheung, T. D.

    2009-08-01

    The Single-Stranded DNA-Binding Protein (RPA) Genes in gamma ray radiation-resistant halophilic archaeon Halobacterium sp. NRC-1 were analyzed in terms of their nucleotide fluctuations. In an ATCG sequence, each base was assigned a number equal to its atomic number. The resulting numerical sequence was the basis of the statistical analysis in this study. Fractal analysis using the Higuchi method gave fractal dimensions of 2.04 and 2.06 for the gene sequences VNG2160 and VNG2162, respectively. The 16S rRNA sequence has a fractal dimension of 1.99. The di-nucleotide Shannon entropy values were found to be negatively correlated with the observed fractal dimensions (R2~ 0.992, N=3). Inclusion of Deinococcus radiodurans Rad-A in the regression analysis decreases the R2 slightly to 0.98 (N=4). A third VNG2163 RPA gene of unknown function but with upregulation activity under irradiation was found to have a fractal dimension of 2.05 and a Shannon entropy of 3.77 bits. The above results are similar to those found in bacterial Deinococcus radiodurans and suggest that their high radiation resistance property would have favored selection of CG di-nucleotide pairs. The two transcription factors TbpD (VNG7114) and TfbA (VNG 2184) were also studied. Using VNG7114, VNG2184, and VNG2163; the regression analysis of fractal dimension versus Shannon entropy shows that R2 ~ 0.997 for N =3. The VNG2163 unknown function may be related to the pathways with transcriptions closely regulated to sequences VNG7114 and VNG2184.

  19. Small-scale angular fluctuations in the microwave background radiation and the existence of isolated large-scale structures in the universe

    International Nuclear Information System (INIS)

    Goicoechea, L.J.; Sanz, J.L.

    1985-01-01

    The relative fluctuation of the present temperature associated with the microwave background radiation (MBR) on a small angular scale, (deltaT/T) 0 , can be related for a general inhomogeneous cosmological model to the kinematical quantities, their gradients, and the Weyl tensor through the geodesic deviation equation. We apply this result to calculate the induction of temperature fluctuations in the MBR by a spherically symmetric cluster (or void) of matter or radiation or both, considered as a perturbation in a flat Friedmann universe, with negligible pressure. For an isolated object (void or cluster) with radius roughly-equal10 3 h -1 Mpc and located outside our present horizon, we have found, taking into account recent data on the anisotropies of the MBR at an angular scale 6 0 , that the relative mass fluctuation is bounded by deltaVertical BarM/MVertical Bar 2 h -1 Mpc and distance from the observer to the center approx. =10h -1 Mpc), the observational angular fluctuations of the MBR imply that deltaVertical BarM/MVertical Bar< or approx. =10%

  20. Incoherent imaging using dynamically scattered coherent electrons

    International Nuclear Information System (INIS)

    Nellist, P.D.; Pennycook, S.J.

    1999-01-01

    We use a Bloch wave approach to show that, even for coherent dynamical scattering from a stationary lattice with no absorption, annular dark-field imaging in a scanning transmission electron microscope gives a direct incoherent structure image of the atomic-column positions of a zone-axis-aligned crystal. Although many Bloch waves may be excited by the probe, the detector provides a filtering effect so that the 1s-type bound states are found to dominate the image contrast for typical experimental conditions. We also find that the column intensity is related to the transverse kinetic energy of the 1s states, which gives atomic number, Z, contrast. The additional effects of phonon scattering are discussed, in particular the reasons why phonon scattering is not a prerequisite for transverse incoherence. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  1. SFERXS, Photoabsorption, Coherent, Incoherent Scattering Cross-Sections Function for Shielding

    International Nuclear Information System (INIS)

    Legarda, F.; Mtz de la Fuente, O.; Herranz, M.

    2002-01-01

    Description of program or function: The use of electromagnetic radiation cross-sections in radiation shielding calculations and more generally in transport theory applications actually requires an interpolation between values which are tabulated for certain values of the energy. In order to facilitate this process and to reduce the computer memory requirements, we have developed, by a least squares method, a set of functions which represents the cross-sections for the photoelectric absorption, the coherent (Rayleigh) and the incoherent (Compton) scattering (1). For this purpose we have accepted as true values the ones tabulated by Storm and Israel (2) for the photoeffect, by Hubbell et Al. (3) for the incoherent scattering and by Hubbell and Overbo (4) for the coherent scattering

  2. Spectral long-range interaction of temporal incoherent solitons.

    Science.gov (United States)

    Xu, Gang; Garnier, Josselin; Picozzi, Antonio

    2014-02-01

    We study the interaction of temporal incoherent solitons sustained by a highly noninstantaneous (Raman-like) nonlinear response. The incoherent solitons exhibit a nonmutual interaction, which can be either attractive or repulsive depending on their relative initial distance. The analysis reveals that incoherent solitons exhibit a long-range interaction in frequency space, which is in contrast with the expected spectral short-range interaction described by the usual approach based on the Raman-like spectral gain curve. Both phenomena of anomalous interaction and spectral long-range behavior of incoherent solitons are described in detail by a long-range Vlasov equation.

  3. Yes, The Precautionary Principle Is Incoherent.

    Science.gov (United States)

    Peterson, Martin

    2017-11-01

    This article is a reply to Thomas Boyer-Kassem's discussion of my criticism of the precautionary principle published in this journal about a decade ago. Boyer-Kassem does not question the logical validity of the theorem proved in my original article, but he brings up important questions about its scope. He also challenges the plausibility of some of the assumptions on which it is based. In this comment, I argue that each objection can be adequately dealt with. As a decision rule, the precautionary principle is (still) incoherent. © 2017 Society for Risk Analysis.

  4. Coherent versus incoherent resonant emission: an experimental method for easy discrimination and measurement

    Science.gov (United States)

    Ceccherini, S.; Colocci, M.; Gurioli, M.; Bogani, F.

    1998-11-01

    The distinction between the coherent and the incoherent component of the radiation emitted from resonantly excited material systems is difficult experimentally, particularly when ultra-short optical pulses are used for excitation. We propose an experimental procedure allowing an easy measurement of the two components. The method is completely general and applicable to any kind of physical system; its feasibility is demonstrated on the resonant emission from excitons in a semiconductor quantum well.

  5. Q2 Dependence of Nuclear Transparency for Incoherent ρ0 Electroproduction

    International Nuclear Information System (INIS)

    John Arrington; Frank Dohrmann; Ahmed El Alaoui; Don Geesaman; Kawtar Hafidi; Roy Holt; Harold Jackson; David Potterveld; Brahim Mustapha; Paul Reimer; Elaine Schulte; Krishni Wijesooriya; Maurik Holtrop; Jacques Ball; Michel Garcon; Jean Laget; Franck Sabatie; Michel Guidal; Latifa Elouadrhiri; Borissov, A.; Wolfgang Lorenzon; Stepan Stepanyan; Lawrence Weinstein

    2002-01-01

    Measurements of exclusive incoherent electroproduction of ρ 0 (770) meson from 2 D, 12 C, and 63 Cu targets up to Q 2 = 4 GeV 2 are proposed using the CLAS detector. The objective of these measurements is to determine the Q 2 dependence of the nuclear transparency ratio for the two nuclear targets: 12 C and 63 Cu at fixed coherence length of quark-antiquark fluctuations of the virtual photon. A sizeable rise of the nuclear transparency is predicted and can be measured in this experiment. A relatively large increase of the nuclear transparency can be considered as a signature of the onset of color transparency

  6. Is the Precautionary Principle Really Incoherent?

    Science.gov (United States)

    Boyer-Kassem, Thomas

    2017-11-01

    The Precautionary Principle has been an increasingly important principle in international treaties since the 1980s. Through varying formulations, it states that when an activity can lead to a catastrophe for human health or the environment, measures should be taken to prevent it even if the cause-and-effect relationship is not fully established scientifically. The Precautionary Principle has been critically discussed from many sides. This article concentrates on a theoretical argument by Peterson (2006) according to which the Precautionary Principle is incoherent with other desiderata of rational decision making, and thus cannot be used as a decision rule that selects an action among several ones. I claim here that Peterson's argument fails to establish the incoherence of the Precautionary Principle, by attacking three of its premises. I argue (i) that Peterson's treatment of uncertainties lacks generality, (ii) that his Archimedian condition is problematic for incommensurability reasons, and (iii) that his explication of the Precautionary Principle is not adequate. This leads me to conjecture that the Precautionary Principle can be envisaged as a coherent decision rule, again. © 2017 Society for Risk Analysis.

  7. Incoherent control of locally controllable quantum systems

    International Nuclear Information System (INIS)

    Dong Daoyi; Zhang Chenbin; Rabitz, Herschel; Pechen, Alexander; Tarn, T.-J.

    2008-01-01

    An incoherent control scheme for state control of locally controllable quantum systems is proposed. This scheme includes three steps: (1) amplitude amplification of the initial state by a suitable unitary transformation, (2) projective measurement of the amplified state, and (3) final optimization by a unitary controlled transformation. The first step increases the amplitudes of some desired eigenstates and the corresponding probability of observing these eigenstates, the second step projects, with high probability, the amplified state into a desired eigenstate, and the last step steers this eigenstate into the target state. Within this scheme, two control algorithms are presented for two classes of quantum systems. As an example, the incoherent control scheme is applied to the control of a hydrogen atom by an external field. The results support the suggestion that projective measurements can serve as an effective control and local controllability information can be used to design control laws for quantum systems. Thus, this scheme establishes a subtle connection between control design and controllability analysis of quantum systems and provides an effective engineering approach in controlling quantum systems with partial controllability information.

  8. Interwell radiative recombination in the presence of random potential fluctuations in GaAs/AlGaAs biased double quantum wells

    DEFF Research Database (Denmark)

    Timofeev, V.B.; Larionov, A.V.; Ioselevich, A.S.

    1998-01-01

    narrowing with temperature increase from 4.5 to 30 K. A theoretical model is presented which explains the observed narrowing in terms of lateral thermally activated tunneling of spatially separated e-h pairs localized by random potential fluctuations in the quantum wells. (C) 1998 American Institute......The interwell radiative recombination from biased double quantum wells (DQW) in pin GaAs/AlGaAs heterostructures is investigated at different temperatures and external electrical fields. The luminescence line of interwell recombination of spatially separated electron-hole pairs exhibits systematic...

  9. A map of the cosmic microwave background radiation from the Wilkinson Microwave Anisotropy Probe (WMAP), showing the large-scale fluctuations (the quadrupole and octopole) isolated by an analysis done partly by theorists at CERN.

    CERN Multimedia

    2004-01-01

    A recent analysis, in part by theorists working at CERN, suggests a new view of the cosmic microwave background radiation. It seems the solar system, rather than the universe, causes the radiation's large-scale fluctuations, similar to the bass in a song.

  10. Coherent and incoherent processes in resonant photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Magnuson, M.; Karis, O.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    In this contribution the authors present the distinction between coherent and incoherent processes in resonant photoemission. As a first step they determine whether an autoionization process is photoemission-like or Auger-like. The discussion is based on measurements for a weakly bonded adsorption system, Ar/Pt(111). This type of system is well adapted to investigate these effects since it yields distinctly shifted spectral features depending on the nature of the process. After this, the question of resonance photoemission in metallic systems is addressed. This is done in connection with measurements at the 2p edges for Ni metal. Ni has been one of the prototype systems for resonant photoemission. The resonances have been discussed in connection with the strong correlation and d-band localization effects in this system. Based on the results some general comments about the appearance of resonant effects in metallic systems are made.

  11. Electromagnetically induced absorption via incoherent collisions

    International Nuclear Information System (INIS)

    Yang Xihua; Sheng Jiteng; Xiao Min

    2011-01-01

    We conduct theoretical studies on electromagnetically induced absorption via incoherent collisions in an inhomogeneously broadened ladder-type three-level system with the density-matrix approach. The effects of the collision-induced coherence decay rates as well as the probe laser field intensity on the probe field absorption are examined. It is shown that with the increase of the collisional decay rates in a moderate range, a narrow dip due to electromagnetically induced transparency superimposed on the Doppler-broadened absorption background can be turned into a narrow peak under the conditions that the probe field intensity is not very weak as compared to the pump field, which results from the enhancement of constructive interference and suppression of destructive interference between one-photon and multiphoton transition pathways. The physical origin of the collision-assisted electromagnetically induced absorption is analyzed with a power-series solution of the density-matrix equations.

  12. Theory of propagation of spectrum and correlations of radiation in optically dense gas in the case of the closed excitation contour

    International Nuclear Information System (INIS)

    Barantsev, K.A.; Litvinov, A.N.; Popov, E.N.

    2017-01-01

    This work is devoted to generalization of the semi-classical theory of interaction of broadband laser radiation with the atomic gas at the room temperature in the cell in the case of the closed excitation contour. The atomic density matrix equations and spectrum and correlations transport equations have been derived for excitation by fluctuating field with Gaussian statistics. It is shown that the spatial oscillations of radiation intensity and atomic density matrix can be excited. It was found that such medium can serve as a filter of incoherent part of the radiation.

  13. Analysis of Ion Composition Estimation Accuracy for Incoherent Scatter Radars

    Science.gov (United States)

    Martínez Ledesma, M.; Diaz, M. A.

    2017-12-01

    The Incoherent Scatter Radar (ISR) is one of the most powerful sounding methods developed to estimate the Ionosphere. This radar system determines the plasma parameters by sending powerful electromagnetic pulses to the Ionosphere and analyzing the received backscatter. This analysis provides information about parameters such as electron and ion temperatures, electron densities, ion composition, and ion drift velocities. Nevertheless in some cases the ISR analysis has ambiguities in the determination of the plasma characteristics. It is of particular relevance the ion composition and temperature ambiguity obtained between the F1 and the lower F2 layers. In this case very similar signals are obtained with different mixtures of molecular ions (NO2+ and O2+) and atomic oxygen ions (O+), and consequently it is not possible to completely discriminate between them. The most common solution to solve this problem is the use of empirical or theoretical models of the ionosphere in the fitting of ambiguous data. More recent works take use of parameters estimated from the Plasma Line band of the radar to reduce the number of parameters to determine. In this work we propose to determine the error estimation of the ion composition ambiguity when using Plasma Line electron density measurements. The sensibility of the ion composition estimation has been also calculated depending on the accuracy of the ionospheric model, showing that the correct estimation is highly dependent on the capacity of the model to approximate the real values. Monte Carlo simulations of data fitting at different signal to noise (SNR) ratios have been done to obtain valid and invalid estimation probability curves. This analysis provides a method to determine the probability of erroneous estimation for different signal fluctuations. Also it can be used as an empirical method to compare the efficiency of the different algorithms and methods on when solving the ion composition ambiguity.

  14. Incidental experiences of affective coherence and incoherence influence persuasion.

    Science.gov (United States)

    Huntsinger, Jeffrey R

    2013-06-01

    When affective experiences are inconsistent with activated evaluative concepts, people experience what is called affective incoherence; when affective experiences are consistent with activated evaluative concepts, people experience affective coherence. The present research asked whether incidental feelings of affective coherence and incoherence would regulate persuasion. Experiences of affective coherence and incoherence were predicted and found to influence the processing of persuasive messages when evoked prior to receipt of such messages (Experiments 1 and 3), and to influence the confidence with which thoughts generated by persuasive messages were held when evoked after presentation of such messages (Experiments 2 and 3). These results extend research on affective coherence and incoherence by showing that they exert a broader impact on cognitive activity than originally assumed.

  15. Incoherent quasielastic neutron scattering from plastic crystals

    International Nuclear Information System (INIS)

    Bee, M.; Amoureux, J.P.

    1980-01-01

    The aim of this paper is to present some applications of a method indicated by Sears in order to correct for multiple scattering. The calculations were performed in the particular case of slow neutron incoherent quasielastic scattering from organic plastic crystals. First, an exact calculation (up to second scattering) is compared with the results of a Monte Carlo simulation technique. Then, an approximation is developed on the basis of a rotational jump model which allows a further analytical treatment. The multiple scattering is expressed in terms of generalized structure factors (which can be regarded as self convolutions of first order structure factors taking into account the instrumental geometry) and lorentzian functions the widths of which are linear combinations of the jump rates. Three examples are given. Two of them correspond to powder samples while in the third we are concerned with the case of a single crystalline slab. In every case, this approximation is shown to be a good approach to the multiple scattering evaluation, its main advantage being the possibility of applying it without any preliminary knowledge of the correlation times for rotational jumps. (author)

  16. Processing oscillatory signals by incoherent feedforward loops

    Science.gov (United States)

    Zhang, Carolyn; Wu, Feilun; Tsoi, Ryan; Shats, Igor; You, Lingchong

    From the timing of amoeba development to the maintenance of stem cell pluripotency,many biological signaling pathways exhibit the ability to differentiate between pulsatile and sustained signals in the regulation of downstream gene expression.While networks underlying this signal decoding are diverse,many are built around a common motif, the incoherent feedforward loop (IFFL),where an input simultaneously activates an output and an inhibitor of the output.With appropriate parameters,this motif can generate temporal adaptation,where the system is desensitized to a sustained input.This property serves as the foundation for distinguishing signals with varying temporal profiles.Here,we use quantitative modeling to examine another property of IFFLs,the ability to process oscillatory signals.Our results indicate that the system's ability to translate pulsatile dynamics is limited by two constraints.The kinetics of IFFL components dictate the input range for which the network can decode pulsatile dynamics.In addition,a match between the network parameters and signal characteristics is required for optimal ``counting''.We elucidate one potential mechanism by which information processing occurs in natural networks with implications in the design of synthetic gene circuits for this purpose. This work was partially supported by the National Science Foundation Graduate Research Fellowship (CZ).

  17. Collective fluctuations in magnetized plasma: Transition probability approach

    International Nuclear Information System (INIS)

    Sosenko, P.P.

    1997-01-01

    Statistical plasma electrodynamics is elaborated with special emphasis on the transition probability approach and quasi-particles, and on modern applications to magnetized plasmas. Fluctuation spectra in the magnetized plasma are calculated in the range of low frequencies (with respect to the cyclotron one), and the conditions for the transition from incoherent to collective fluctuations are established. The role of finite-Larmor-radius effects and particle polarization drift in such a transition is explained. The ion collective features in fluctuation spectra are studied. 63 refs., 30 figs

  18. Quantum fluctuations

    International Nuclear Information System (INIS)

    Reynaud, S.; Giacobino, S.; Zinn-Justin, J.

    1997-01-01

    This course is dedicated to present in a pedagogical manner the recent developments in peculiar fields concerned by quantum fluctuations: quantum noise in optics, light propagation through dielectric media, sub-Poissonian light generated by lasers and masers, quantum non-demolition measurements, quantum electrodynamics applied to cavities and electrical circuits involving superconducting tunnel junctions. (A.C.)

  19. Whole-body intravoxel incoherent motion imaging

    Energy Technology Data Exchange (ETDEWEB)

    Filli, Lukas; Wurnig, Moritz C.; Eberhardt, Christian; Guggenberger, Roman; Boss, Andreas [University Hospital Zurich, Department of Radiology, Zurich (Switzerland); Luechinger, Roger [University and ETH Zurich, Institute of Biomedical Technology, Zurich (Switzerland)

    2015-07-15

    To investigate the technical feasibility of whole-body intravoxel incoherent motion (IVIM) imaging. Whole-body MR images of eight healthy volunteers were acquired at 3T using a spin-echo echo-planar imaging sequence with eight b-values. Coronal parametrical whole-body maps of diffusion (D), pseudodiffusion (D*), and the perfusion fraction (F{sub p}) were calculated. Image quality was rated qualitatively by two independent radiologists, and inter-reader reliability was tested with intra-class correlation coefficients (ICCs). Region of interest (ROI) analysis was performed in the brain, liver, kidney, and erector spinae muscle. Depiction of anatomic structures was rated as good on D maps and good to fair on D* and F{sub p} maps. Exemplary mean D (10{sup -3} mm{sup 2}/s), D* (10{sup -3} mm{sup 2}/s) and F{sub p} (%) values (± standard deviation) of the renal cortex were as follows: 1.7 ± 0.2; 15.6 ± 6.5; 20.9 ± 4.4. Inter-observer agreement was ''substantial'' to ''almost perfect'' (ICC = 0.80 - 0.92). The coefficient of variation of D* was significantly lower with the proposed algorithm compared to the conventional algorithm (p < 0.001), indicating higher stability. The proposed IVIM protocol allows computation of parametrical maps with good to fair image quality. Potential future clinical applications may include characterization of widespread disease such as metastatic tumours or inflammatory myopathies. (orig.)

  20. CINCH (confocal incoherent correlation holography) super resolution fluorescence microscopy based upon FINCH (Fresnel incoherent correlation holography).

    Science.gov (United States)

    Siegel, Nisan; Storrie, Brian; Bruce, Marc; Brooker, Gary

    2015-02-07

    FINCH holographic fluorescence microscopy creates high resolution super-resolved images with enhanced depth of focus. The simple addition of a real-time Nipkow disk confocal image scanner in a conjugate plane of this incoherent holographic system is shown to reduce the depth of focus, and the combination of both techniques provides a simple way to enhance the axial resolution of FINCH in a combined method called "CINCH". An important feature of the combined system allows for the simultaneous real-time image capture of widefield and holographic images or confocal and confocal holographic images for ready comparison of each method on the exact same field of view. Additional GPU based complex deconvolution processing of the images further enhances resolution.

  1. Generation and spectroscopic signatures of a fractional quantum Hall liquid of photons in an incoherently pumped optical cavity

    Science.gov (United States)

    Umucalılar, R. O.; Carusotto, I.

    2017-11-01

    We investigate theoretically a driven dissipative model of strongly interacting photons in a nonlinear optical cavity in the presence of a synthetic magnetic field. We show the possibility of using a frequency-dependent incoherent pump to create a strongly correlated ν =1 /2 bosonic Laughlin state of light: Due to the incompressibility of the Laughlin state, fluctuations in the total particle number and excitation of edge modes can be tamed by imposing a suitable external potential profile for photons. We further propose angular-momentum-selective spectroscopy of the emitted light as a tool to obtain unambiguous signatures of the microscopic physics of the quantum Hall liquid of light.

  2. Towards sub-{Angstrom} resolution through incoherent imaging

    Energy Technology Data Exchange (ETDEWEB)

    Pennycook, S.J.; Chisholm, M.F. [Oak Ridge National Lab., TN (United States); Nellist, P.D. [Cavendish Lab., Cambridge, (United Kingdom)

    1997-04-01

    As first pointed out by Lord Rayleigh a century ago, incoherent imaging offers a substantial resolution enhancement compared to coherent imaging, together with freedom from phase contrast interference effects and contrast oscillations. In the STEM configuration, with a high angle annular detector to provide the transverse incoherence, the image also shows strong Z-contrast, sufficient in the case of a 300 kV STEM to image single Pt and Rh atoms on a {gamma}-alumina support. The annular detector provides complementarity to a bright field detector of the same size. For weakly scattering specimens, it shows greater contrast than the incoherent bright field image, and also facilitates EELS analysis at atomic resolution, using the Z-contrast image to locate the probe with sub-{angstrom} precision. The inner radius of the annular detector can be chosen to reduce the transverse coherence length to well below the spacings needed to resolve the object, a significant advantage compared to light microscopy.

  3. Coherent and incoherent (μ-, e-) conversion in nuclei

    International Nuclear Information System (INIS)

    Chiang, H.C.; Oset, E.; Kosmas, T.S.; Faessler, A.; Vergados, J.D.

    1993-01-01

    Coherent and incoherent (μ - , e - ) conversion in nuclei is studied within the framework of several theories which violate flavour lepton number. A useful approach is followed which allows a factorization of the conversion widths into nuclear factors and other factors which depend only on the elementary process. The nuclear factors are evaluated in a wide range of nuclei allowing simple calculations of the conversion rates throughout the periodic table for a given theory with a minimum of work in the elementary sector. The coherent conversion is found to dominate the process. The results obtained modify appreciable previous results in the literature, particularly in the incoherent process. (orig.)

  4. Incoherent transport for phases that spontaneously break translations

    Science.gov (United States)

    Donos, Aristomenis; Gauntlett, Jerome P.; Griffin, Tom; Ziogas, Vaios

    2018-04-01

    We consider phases of matter at finite charge density which spontaneously break spatial translations. Without taking a hydrodynamic limit we identify a boost invariant incoherent current operator. We also derive expressions for the small frequency behaviour of the thermoelectric conductivities generalising those that have been derived in a translationally invariant context. Within holographic constructions we show that the DC conductivity for the incoherent current can be obtained from a solution to a Stokes flow for an auxiliary fluid on the black hole horizon combined with specific thermodynamic quantities associated with the equilibrium black hole solutions.

  5. Nanometer-scale elongation rate fluctuations in the Myriophyllum aquaticum (Parrot feather) stem were altered by radio-frequency electromagnetic radiation.

    Science.gov (United States)

    Senavirathna, Mudalige Don Hiranya Jayasanka; Asaeda, Takashi; Thilakarathne, Bodhipaksha Lalith Sanjaya; Kadono, Hirofumi

    2014-01-01

    The emission of radio-frequency electromagnetic radiation (EMR) by various wireless communication base stations has increased in recent years. While there is wide concern about the effects of EMR on humans and animals, the influence of EMR on plants is not well understood. In this study, we investigated the effect of EMR on the growth dynamics of Myriophyllum aquaticum (Parrot feather) by measuring the nanometric elongation rate fluctuation (NERF) using a statistical interferometry technique. Plants were exposed to 2 GHz EMR at a maximum of 1.42 Wm(-2) for 1 h. After continuous exposure to EMR, M. aquaticum plants exhibited a statistically significant 51 ± 16% reduction in NERF standard deviation. Temperature observations revealed that EMR exposure did not cause dielectric heating of the plants. Therefore, the reduced NERF was due to a non-thermal effect caused by EMR exposure. The alteration in NERF continued for at least 2.5 h after EMR exposure and no significant recovery was found in post-EMR NERF during the experimental period.

  6. Atomic form factors, incoherent scattering functions, and photon scattering cross sections

    International Nuclear Information System (INIS)

    Hubbell, J.H.; Veigele, W.J.; Briggs, E.A.; Brown, R.T.; Cromer, D.T.; Howerton, R.J.

    1975-01-01

    Tabulations are presented of the atomic form factor, F (α,Z), and the incoherent scattering function, S (x,Z), for values of x (=sin theta/2)/lambda) from 0.005 A -1 to 10 9 A -1 , for all elements A=1 to 100. These tables are constructed from available state-of-the-art theoretical data, including the Pirenne formulas for Z=1, configuration-into action results by Brown using Brown-Fontana and Weiss correlated wavefunctions for Z=2 to 6 non-relativistic Hartree-Fock results by Cromer for Z=7 to 100 and a relativistic K-shell analytic expression for F (x,Z) by Bethe Levinger for x>10 A -1 for all elements Z=2 to 100. These tabulated values are graphically compared with available photon scattering angular distribution measurements. Tables of coherent (Rayleigh) and incoherent (Compton) total scattering cross sections obtained by nummerical integration over combinations of F 2 (x,Z) with the Thomson formula and S (x,Z) with the Klum-Nishina Formual, respectively, are presented for all elements Z=1 to 100, for photon energies 100 eV (lambda=124 A) to 100 MeV (0.000124 A). The incoherent scattering cross sections also include the radiative and double-Compton corrections as given by Mork. Similar tables are presented for the special cases of terminally-bonded hydrogen and for the H 2 molecule, interpolated and extrapolated from values calculated by Stewart et al., and by Bentley and Stewart using Kolos-Roothaan wavefunctions

  7. Interfacial Energy and Fine Defect Structures for Incoherent Films

    OpenAIRE

    Cermelli, Paolo; Gurtin, Morton E.; Leoni, Giovanni

    1999-01-01

    This note summarizes recent results in which modern techniques of the calculus of variations are used to obtain qualitative features of film-substrate interfaces for a broad class of interfacial energies. In particular, we show that the existence of a critical thickness for incoherency and the formation of interfacial dislocations depend strongly on the convexity and smoothness of the interfacial energy function.

  8. Optically transparent multiple access networks employing incoherent spectral codes

    NARCIS (Netherlands)

    Huiszoon, B.

    2008-01-01

    This Ph.D. thesis is divided into 7 chapters to provide the reader an overview of the main results achieved in di®erent sub-topics of the study towards optically transparent multiple access networks employing incoherent spectral codes taking into account wireless transmission aspects. The work

  9. Fluctuation analysis

    International Nuclear Information System (INIS)

    Clarke, J.

    1980-01-01

    This paper briefly reviews sources of noise in Josephson junctions, and the limits they impose on the sensitivity of dc and rf SQUIDS. The results are strictly valid only for a resistively shunted junction (RSJ) with zero capacitance, but should be applicable to point contact junctions and microbridges in so far as these devices can be approximated by the RSJ model. Fluctuations arising from Nyquist noise in the resistive shunt of a single junction are discussed in the limit eI/sub o/R/k/sub B/T << 1 in which a classical treatment is appropriate, and then extend the treatment to the limit eI/sub o/R/k/sub B/T greater than or equal to 1 in which quantum effects become important. The Nyquist limit theory is used to calculate the noise in a dc SQUID, and the results are compared with a number of practical devices. The quantum limit is briefly considered. Results for the predicted sensitivity of rf SQUIDS are presented, and also compared with a number of practical devices. Finally, the importance of l/f noise (f is the frequency) in limiting the low frequency performance of SQUIDS is discussed

  10. Quantum imaging with incoherently scattered light from a free-electron laser

    Science.gov (United States)

    Schneider, Raimund; Mehringer, Thomas; Mercurio, Giuseppe; Wenthaus, Lukas; Classen, Anton; Brenner, Günter; Gorobtsov, Oleg; Benz, Adrian; Bhatti, Daniel; Bocklage, Lars; Fischer, Birgit; Lazarev, Sergey; Obukhov, Yuri; Schlage, Kai; Skopintsev, Petr; Wagner, Jochen; Waldmann, Felix; Willing, Svenja; Zaluzhnyy, Ivan; Wurth, Wilfried; Vartanyants, Ivan A.; Röhlsberger, Ralf; von Zanthier, Joachim

    2018-02-01

    The advent of accelerator-driven free-electron lasers (FEL) has opened new avenues for high-resolution structure determination via diffraction methods that go far beyond conventional X-ray crystallography methods. These techniques rely on coherent scattering processes that require the maintenance of first-order coherence of the radiation field throughout the imaging procedure. Here we show that higher-order degrees of coherence, displayed in the intensity correlations of incoherently scattered X-rays from an FEL, can be used to image two-dimensional objects with a spatial resolution close to or even below the Abbe limit. This constitutes a new approach towards structure determination based on incoherent processes, including fluorescence emission or wavefront distortions, generally considered detrimental for imaging applications. Our method is an extension of the landmark intensity correlation measurements of Hanbury Brown and Twiss to higher than second order, paving the way towards determination of structure and dynamics of matter in regimes where coherent imaging methods have intrinsic limitations.

  11. On the response of large dams to incoherent seismic excitation

    International Nuclear Information System (INIS)

    Ramadan, O.; Novak, M.

    1993-01-01

    An intensive parametric study was conducted to investigate the response of concrete gravity dams to horizontal, spatially variable seismic ground motions. Both segmented dams consisting of separate blocks, or monoliths, and continuous monolithic dams are considered. The study includes the effects of various parameters on system natural frequencies, vibration modes, modal displacement ratios, as well as dam displacements and internal stresses due to spatially variable ground motions. The dam analytical model, and dam response to incoherent ground motions are described. The results show that the dam vibrates almost as a rigid body under the fully correlated waves, but bends and twists significantly under the spatially correlated motions. Dam-foundation interaction magnifies the low frequency components of the dam response, more so for a full reservoir, but decreases the high frequency components. For long dams, the effects of spatially incoherent ground motions are qualitatively different and can be much greater than those due to surface travelling waves. 3 refs., 3 figs

  12. Incoherently combining logarithmic aspheric lenses for extended depth of field.

    Science.gov (United States)

    Chu, Kaiqin; George, Nicholas; Chi, Wanli

    2009-10-01

    We describe a method for combining concentric logarithmic aspheric lenses in order to obtain an extended depth of field. Substantial improvement in extending the depth of field is obtained by carefully controlling the optical path difference among the concentric lenses so that their outputs combine incoherently. The system is analyzed through diffraction theory and the point spread function is shown to be highly invariant over a long range of object distances. After testing the image performance on a three-dimensional scene, we found that the incoherently combined logarithmic aspheres can provide a high-quality image over an axial distance corresponding to a defocus of +/- 14(lambda/4). Studies of the images of two-point objects are presented to illustrate the resolution of these lenses.

  13. Coherent and Incoherent Neutral Current Scattering for Supernova Detection

    Directory of Open Access Journals (Sweden)

    P. C. Divari

    2012-01-01

    Full Text Available The total cross sections as well as the neutrino event rates are calculated in the neutral current neutrino scattering off 40Ar and 132Xe isotopes at neutrino energies (Ev<100 MeV. The individual contribution coming from coherent and incoherent channels is taking into account. An enhancement of the neutral current component is achieved via the coherent (0gs+→0gs+ channel which is dominant with respect to incoherent (0gs+→Jf one. The response of the above isotopes as a supernova neutrino detection has been considered, assuming a two parameter Fermi-Dirac distribution for the supernova neutrino energy spectra. The calculated total cross sections are tested on a gaseous spherical TPC detector dedicated for supernova neutrino detection.

  14. Phase diagram of incoherently driven strongly correlated photonic lattices

    Science.gov (United States)

    Biella, Alberto; Storme, Florent; Lebreuilly, José; Rossini, Davide; Fazio, Rosario; Carusotto, Iacopo; Ciuti, Cristiano

    2017-08-01

    We explore theoretically the nonequilibrium photonic phases of an array of coupled cavities in presence of incoherent driving and dissipation. In particular, we consider a Hubbard model system where each site is a Kerr nonlinear resonator coupled to a two-level emitter, which is pumped incoherently. Within a Gutzwiller mean-field approach, we determine the steady-state phase diagram of such a system. We find that, at a critical value of the intercavity photon hopping rate, a second-order nonequilibrium phase transition associated with the spontaneous breaking of the U(1 ) symmetry occurs. The transition from an incompressible Mott-like photon fluid to a coherent delocalized phase is driven by commensurability effects and not by the competition between photon hopping and optical nonlinearity. The essence of the mean-field predictions is corroborated by finite-size simulations obtained with matrix product operators and corner-space renormalization methods.

  15. Neutron scattering in disordered alloys: coherent and incoherent intensities

    International Nuclear Information System (INIS)

    Mookerjee, A.; Yussouff, M.

    1985-02-01

    A priori it is not clear how to split the total intensity of thermal neutron scattering from disordered alloys into a coherent and an incoherent part. We present here a formalism to do this. The formalism is based on the augmented space technique introduced earlier by one of the authors. It includes disorder in mass, force constants and scattering lengths. A self-consistent CCPA which is tractable for realistic calculations is presented for the coherent and incoherent intensities. This is expected to prove useful in theoretically analysis data for alloys (e.g. Nisub(x)Ptsub(1-x), Nisub(x)Pdsub(1-x), Nisub(x)Crsub(1-x)) for which it is necessary to go beyond the usual single site CPAs for reliable accuracy. (author)

  16. Charge Fluctuations of an Uncharged Black Hole

    OpenAIRE

    Schiffer, Marcelo

    2016-01-01

    In this paper we calculate charge fluctuations of a Schwarzschild black-hole of mass $M$ confined within a perfectly reflecting cavity of radius R in thermal equilibrium with various species of radiation and fermions . Charge conservation is constrained by a Lagrange multiplier (the chemical potential). Black hole charge fluctuations are expected owing to continuous absorption and emission of particles by the black hole. For black holes much more massive than $10^{16} g$ , these fluctuations ...

  17. Incoherent scatter studies of upper atmosphere dynamics and coding technique

    International Nuclear Information System (INIS)

    Haeggstroem, Ingemar.

    1990-09-01

    Observations by the EISCAT incoherent scatter radar are used to study the dynamics of the auroral upper atmosphere. The study describes some effects of the strong plasma convection occurring at these latitudes and a new coding technique for incoherent scatter radars. A technique to determine the thermospheric neutral wind from incoherent scatter measurements is described. Simultaneous Fabry-Perot interferometer measurements of the wind are compared with those derived from the radar data. F-region electron density depletions in the afternoon/evening sector of the auroral zone, identified as the main ionospheric trough, are investigated. In a statistical study, based on wide latitude scanning experiment made at solar minimum, the trough appearance at a given latitude is compared to the geomagnetic index K p , and an empirical model predicting the latitude of the trough is proposed. Detailed studies, using different experiment modes, show that the equatorward edge of the auroral oval is co-located of up to 1 degree poleward of the trough minimum, which in turn is co-located with the peak convective electric field, with its boundary 1 degree - 2 degree equatorward of the trough minimum. It is shown that the F-region ion composition changes from pure 0 + to molecular ion dominated (NO + /O 2 + ) as the trough moves into the region probed by the radar. In a special case, where a geomagnetic sudden impulse caused an expansion of the plasma convection pattern, the equatorward trough progression is studied together with ionosonde measurements. A new coding technique for incoherent scatter radar measurement is introduced and described. The method, called alternating codes, provides significantly more accurate estimates of the plasma parameters than can be obtained by frequency commutated multipulse measurements. Simple explanations of the method are given as well as a precise definition. Two examples of application of the alternating codes are presented, showing the high

  18. Are Ascriptions of Intentionality to the Brain Incoherent?

    DEFF Research Database (Denmark)

    Presskorn-Thygesen, Thomas

    The ascriptions of ‘agency’ or ‘intentionality’ to the brain has long been regarded with suspicion from social scientists and philosophers. In the talk, I will argue that this suspicion is perfectly legitimate and that the standard response from the defenders of cognitive neuroscience is illegiti...... to the brain are conceptually incoherent because it commits a mereological fallacy (Bennett&Hacker 2001, 2007)....

  19. Holographic fluorescence microscopy with incoherent digital holographic adaptive optics.

    Science.gov (United States)

    Jang, Changwon; Kim, Jonghyun; Clark, David C; Lee, Seungjae; Lee, Byoungho; Kim, Myung K

    2015-01-01

    Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: selfinterference incoherent digital holography (SIDH). The SIDH generates a complex—i.e., amplitude plus phase—hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.

  20. Electromagnetically induced two-dimensional grating assisted by incoherent pump

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang, E-mail: wrg@snnu.edu.cn

    2017-04-25

    We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication. - Highlights: • Two-dimensional grating is coherently induced in four-level atoms. • Phase and gain-phase gratings are obtained assisted by incoherent pump. • The diffraction power is improved due to the enhanced refraction modulation. • The gratings can be utilized as multi-channel all-optical splitter and router.

  1. Coherent imaging with incoherent light in digital holographic microscopy

    Science.gov (United States)

    Chmelik, Radim

    2012-01-01

    Digital holographic microscope (DHM) allows for imaging with a quantitative phase contrast. In this way it becomes an important instrument, a completely non-invasive tool for a contrast intravital observation of living cells and a cell drymass density distribution measurement. A serious drawback of current DHMs is highly coherent illumination which makes the lateral resolution worse and impairs the image quality by a coherence noise and a parasitic interference. An uncompromising solution to this problem can be found in the Leith concept of incoherent holography. An off-axis hologram can be formed with arbitrary degree of light coherence in systems equipped with an achromatic interferometer and thus the resolution and the image quality typical for an incoherent-light wide-field microscopy can be achieved. In addition, advanced imaging modes based on limited coherence can be utilized. The typical example is a coherence-gating effect which provides a finite axial resolution and makes DHM image similar to that of a confocal microscope. These possibilities were described theoretically using the formalism of three-dimensional coherent transfer functions and proved experimentally by the coherence-controlled holographic microscope which is DHM based on the Leith achromatic interferometer. Quantitative-phase-contrast imaging is demonstrated with incoherent light by the living cancer cells observation and their motility evaluation. The coherence-gating effect was proved by imaging of model samples through a scattering layer and living cells inside an opalescent medium.

  2. Annealing characteristics of SiO2-Si structures after incoherent light pulse processing

    International Nuclear Information System (INIS)

    Sieber, N.; Klabes, R.; Voelskow, M.; Fenske, F.

    1982-01-01

    The behaviour of oxide charges and interface charges in boron implanted and non-implanted SiO 2 -Si structures as well as the electrical activation of the dopants by the action of incoherent light pulses was studied. Depth profiles of electrically active boron ions are presented for different annealing conditions as measured by the pulsed C-V method. It can be concluded that exposure of MOS structures to intense radiation of flash lamps does not increase the fixed charge and the fast state density at the SiO 2 -Si interface if optimal annealing conditions (energy densities) are employed. Low dose boron implanted silicon can be electrically activated without diffusion or segregation of dopants

  3. He{sup 2+} HEATING VIA PARAMETRIC INSTABILITIES OF PARALLEL PROPAGATING ALFVÉN WAVES WITH AN INCOHERENT SPECTRUM

    Energy Technology Data Exchange (ETDEWEB)

    He, Peng; Gao, Xinliang; Lu, Quanming; Wang, Shui, E-mail: gaoxl@mail.ustc.edu.cn [CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei 230026 (China)

    2016-08-10

    The preferential heating of heavy ions in the solar corona and solar wind has been a long-standing hot topic. In this paper we use a one-dimensional hybrid simulation model to investigate the heating of He{sup 2+} particles during the parametric instabilities of parallel propagating Alfvén waves with an incoherent spectrum. The evolution of the parametric instabilities has two stages and involves the heavy ion heating during the entire evolution. In the first stage, the density fluctuations are generated by the modulation of the pump Alfvén waves with a spectrum, which then results in rapid coupling with the pump Alfvén waves and the cascade of the magnetic fluctuations. In the second stage, each pump Alfvén wave decays into a forward density mode and a backward daughter Alfvén mode, which is similar to that of a monochromatic pump Alfvén wave. In both stages the perpendicular heating of He{sup 2+} particles occurs. This is caused by the cyclotron resonance between He{sup 2+} particles and the high-frequency magnetic fluctuations, whereas the Landau resonance between He{sup 2+} particles and the density fluctuations leads to the parallel heating of He{sup 2+} particles. The influence of the drift velocity between the protons and the He{sup 2+} particles on the heating of He{sup 2+} particles is also discussed in this paper.

  4. Fluctuations in quantum chaos

    International Nuclear Information System (INIS)

    Casati, G.; Chirikov, B.V.

    1996-01-01

    Various fluctuations in quantum systems with discrete spectrum are discussed, including recent unpublished results. Open questions and unexplained peculiarities of quantum fluctuations are formulated [ru

  5. Reconstruction of an Non-Monochromatically Illuminated Object Imaged through an Electron Microscope with a Fluctuating Electromagnetic Field

    NARCIS (Netherlands)

    Hoenders, B.J.

    1975-01-01

    It is shown that a weak phase object imaged by an electron microscope within the presence of instabilities of the lense currents and the acceleration voltage, fluctuating electromagnetic field, can be reconstructed from the intensity distribution in the image plane. Perfectly incoherent illumination

  6. Experimental tests of induced spatial incoherence using short laser wavelength

    International Nuclear Information System (INIS)

    Obenschain, S.P.; Grun, J.; Herbst, M.J.

    1986-01-01

    The authors have developed a laser beam smoothing technique called induced spatial incoherence (ISI), which can produce the highly uniform focal profiles required for direct-drive laser fusion. Uniform well-controlled focal profiles are required to obtain the highly symmetric pellet implosions needed for high-energy gain. In recent experiments, the authors' tested the effects of ISI on high-power laser-target interaction. With short laser wavelength, the coupling physics dramatically improved over that obtained with an ordinary laser beam

  7. Impact of Microwaves on the Electron Cloud and Incoherent Effects

    CERN Document Server

    Decker, Franz Josef; Zimmermann, Frank

    2002-01-01

    We consider the use of microwaves for manipulating the electron cloud, describing an exploratory experiment at PEP-II as well as computer simulations of the electron cloud build-up in the presence of a microwave for an LHC dipole. We then show that the incoherent effects of the electron cloud - energy loss and transverse emittance growth due to scattering of the electrons - are negligible. This suggests that the disturbance of the coherent motion may be another possible application of microwaves, which could prevent beam emittance growth and beam loss.

  8. Semidiurnal tide in the E region from incoherent scatter measurements at Arecibo

    International Nuclear Information System (INIS)

    Wand, R.H.

    1976-01-01

    A five-pulse technique was implemented for the 430 MHz incoherent scatter radar at Arecibo Observatory (18.3 0 N) to explore the detailed thermal structure of the E region from 105 to 130 km with an altitude resolution of 3 km. Five days of measurements in Sept-Oct 1970 showed long-period temperature fluctuations having a downward phase progression. The temperature oscillations are interpreted as manifestations of a semidiurnal tide which is quite stable over a 12-day period, together with a superimposed spectrum of shorter-period gravity waves which are randomly phased from day to day. The semidiurnal tide increased to a maximum amplitude of 17 percent of the mean temperature near 115 km and decreased above this altitude as dissipative effects became important. The vertical wavelength, deduced from the altitude variation of semidiurnal tidal phase, showed a smooth increase from about 20 km at an altitude of 109 km to about 50 km at an altitude of 127 km. No ready interpretation of the observed tidal characteristics was possible in terms of present theories for the semidiurnal tide. Altitude profiles of mean daytime temperature and ion-neutral collision frequency were also obtained from the measurements. The mean temperature gradient between 115 and 130 km was 15 K/km, which is somewhat larger than that given by current atmospheric models

  9. The role of incoherent microRNA-mediated feedforward loops in noise buffering.

    Directory of Open Access Journals (Sweden)

    Matteo Osella

    2011-03-01

    Full Text Available MicroRNAs are endogenous non-coding RNAs which negatively regulate the expression of protein-coding genes in plants and animals. They are known to play an important role in several biological processes and, together with transcription factors, form a complex and highly interconnected regulatory network. Looking at the structure of this network, it is possible to recognize a few overrepresented motifs which are expected to perform important elementary regulatory functions. Among them, a special role is played by the microRNA-mediated feedforward loop in which a master transcription factor regulates a microRNA and, together with it, a set of target genes. In this paper we show analytically and through simulations that the incoherent version of this motif can couple the fine-tuning of a target protein level with an efficient noise control, thus conferring precision and stability to the overall gene expression program, especially in the presence of fluctuations in upstream regulators. Among the other results, a nontrivial prediction of our model is that the optimal attenuation of fluctuations coincides with a modest repression of the target expression. This feature is coherent with the expected fine-tuning function and in agreement with experimental observations of the actual impact of a wide class of microRNAs on the protein output of their targets. Finally, we describe the impact on noise-buffering efficiency of the cross-talk between microRNA targets that can naturally arise if the microRNA-mediated circuit is not considered as isolated, but embedded in a larger network of regulations.

  10. Interwell Radiative Recombination in the Presence of Random Potential Fluctuations in GaAs/AlGaAs Biased Double Quantum Wells

    DEFF Research Database (Denmark)

    Timofeev, V.B.; Larionov, A.V.; Ioselevich, A.S.

    1999-01-01

    The interwell luminescence (PL) of spatially separated e-h pairs exhibits systematic narrowing with temperature increase which are explained in terms of lateral thermo-activated tunneling of e-h pairs localized by random potential fluctuations (RPF). At critical temperatures the quasi-equilibrium......The interwell luminescence (PL) of spatially separated e-h pairs exhibits systematic narrowing with temperature increase which are explained in terms of lateral thermo-activated tunneling of e-h pairs localized by random potential fluctuations (RPF). At critical temperatures the quasi......-equilibrium of carriers, undergoes an abrupt transition. This occurs with significant redistribution of the electrical field inside the structure and give rise to a low frequency noice appearing in the luminescence. Below critical temperature the new steady state results in the accumulation of 2DEG in one of the well....

  11. Intersubassembly incoherencies and grouping techniques in LMFBR hypothetical overpower accident

    International Nuclear Information System (INIS)

    Wilburn, N.P.

    1977-10-01

    A detailed analysis was made of the FTR core using the 100-channel MELT-IIIA code. Results were studied for the transient overpower accident (where 0.5$/sec and 1$/sec ramps) and in which the Damage Parameter and the Failure Potential criteria were used. Using the information obtained from these series of runs, a new method of grouping the subassemblies into channels has been developed. Also, it was demonstrated that a 7-channel representation of the FTR core using this method does an adequate job of representing the behavior during a hypothetical disruptive transient overpower core accident. It has been shown that this new 7-channel grouping method does a better job than an earlier 20-channel grouping. It has also been demonstrated that the incoherency effects between subassemblies as shown during the 76-channel representation of the reactor can be adequately modeled by 7-channels, provided the 7-channels are selected according to the criteria stated in the report. The overall results of power and net reactivity were shown to be only slightly different in the two cases of the 7-channel and the 76-channel runs. Therefore, it can be concluded that any intersubassembly incoherencies can be modeled adequately by a small number of channels, provided the subassemblies making up these channels are selected according to the criteria stated

  12. QR code optical encryption using spatially incoherent illumination

    Science.gov (United States)

    Cheremkhin, P. A.; Krasnov, V. V.; Rodin, V. G.; Starikov, R. S.

    2017-02-01

    Optical encryption is an actively developing field of science. The majority of encryption techniques use coherent illumination and suffer from speckle noise, which severely limits their applicability. The spatially incoherent encryption technique does not have this drawback, but its effectiveness is dependent on the Fourier spectrum properties of the image to be encrypted. The application of a quick response (QR) code in the capacity of a data container solves this problem, and the embedded error correction code also enables errorless decryption. The optical encryption of digital information in the form of QR codes using spatially incoherent illumination was implemented experimentally. The encryption is based on the optical convolution of the image to be encrypted with the kinoform point spread function, which serves as an encryption key. Two liquid crystal spatial light modulators were used in the experimental setup for the QR code and the kinoform imaging, respectively. The quality of the encryption and decryption was analyzed in relation to the QR code size. Decryption was conducted digitally. The successful decryption of encrypted QR codes of up to 129  ×  129 pixels was demonstrated. A comparison with the coherent QR code encryption technique showed that the proposed technique has a signal-to-noise ratio that is at least two times higher.

  13. The Precautionary Principle Has Not Been Shown to Be Incoherent: A Reply to Peterson : Response

    NARCIS (Netherlands)

    Boyer-Kassem, Thomas

    2017-01-01

    In this journal, I have objected to Peterson's 2006 claim that the precautionary principle is an incoherent decision rule. I defend my objections to Peterson's recent replies, and I still claim that the precautionary principle has not been shown to be incoherent.

  14. The Precautionary Principle Has Not Been Shown to Be Incoherent: A Reply to Peterson.

    Science.gov (United States)

    Boyer-Kassem, Thomas

    2017-11-01

    In this journal, I have objected to Peterson's 2006 claim that the precautionary principle is an incoherent decision rule. I defend my objections to Peterson's recent replies, and I still claim that the precautionary principle has not been shown to be incoherent. © 2017 Society for Risk Analysis.

  15. Resolution of coherent and incoherent imaging systems reconsidered : Classical criteria and a statistical alternative

    NARCIS (Netherlands)

    Van Aert, S.; Van Dyck, D.; Den Dekker, A.J.

    2006-01-01

    The resolution of coherent and incoherent imaging systems is usually evaluated in terms of classical resolution criteria, such as Rayleigh’s. Based on these criteria, incoherent imaging is generally concluded to be ‘better’ than coherent imaging. However, this paper reveals some misconceptions in

  16. Radiation induced homogeneous precipitation in undersaturated solid-solutions

    International Nuclear Information System (INIS)

    Cauvin, R.; Martin, G.

    1979-01-01

    A TEM study of 1 MeV electron irradiated Al 1.9 at% Zn solid solution shows that Zn precipitates form, under irradiation at temperatures well above the Zn solvus temperature outside irradiation. The corresponding upward shift of this temperature is dose rate dependent. This new example of radiation-induced precipitation exhibits unexpected features, which are not accounted for by the available models: (1) no correlation exists between the location of the precipitates and that of the point defects sinks; (2) the precipitation of incoherent β-phase with atomic volume smaller than that of the matrix, and of coherent G.P. zones both occurs; (3) the size of the coherent β precipitates saturates at large dose. A general mechanism for solute concentration fluctuations under irradiation is proposed which qualitatively accounts for the formation of coherent G.P. zones and for the nucleation of solute clusters with more complex structures. A reanalysis of Russell's model (1977) for the growth of incoherent precipitates shows that it may qualitatively account for the observed behavior of the β phase precipitates. (Auth.)

  17. Some fundamental aspects of fluctuations and coherence in charged-particle beams in storage rings

    International Nuclear Information System (INIS)

    Chattopadhyay, S.

    1984-01-01

    A conceptual survey and exposition is presented of some fundamental aspects of fluctuations and coherence, as well as the interplay between the two, in coasting charged-particle beams - both continuous and bunched - in storage rings. A detailed study is given of the spectral properties of the incoherent phase-space Schottky fluctuations, their propagation as waves in the beam, and the analytic complex coherent beam electromagnetic response or transfer function. The modification or distortion of these by collective interactions is examined in terms of simple regeneration mechanisms. Collective or coherent forces in the beam-storage-ring system are described by defining suitable impedance functions or propagators, and a brief discussion of the coherent collective modes and their stability is provided, including a general and rigorous description of the Nyquist stability criterion. The nature of the critical fluctuations near an instability threshold is explored. The concept of Landau damping and its connection with phase-mixing within the beam is outlined. The important connection between the incoherent fluctuations and the beam response, namely the Fluctuation-Dissipation relation, is revealed. A brief discussion is given of the information degrees of freedom, and effective temperature of the fluctuation signals. Appendices provide a short resume of some general aspects of various interactions in a charged-particle beam-environment system in a storage ring and a general introduction to kinetic theory as applied to particle beams. (orig.)

  18. Fluctuations in the cosmic microwave background

    International Nuclear Information System (INIS)

    Banday, A.J.; Wolfendale, A.W.

    1990-01-01

    In view of the importance to contemporary cosmology, and to our understanding of the Universe, of the precise nature of the Cosmic Microwave Background (CMB) spectrum, we consider the effects on this spectrum of contamination by other radiation fields of both galactic and extragalactic origin. Particular attention is given to the significance of measurements of the fluctuations in the 'background' radiation detected at 10.46 GHz and we conclude that these fluctuations are of the same magnitude as those expected from galactic cosmic-ray effects. A more detailed study of the cosmic-ray induced fluctuations and measurements at higher frequencies will be needed before genuine CMB fluctuations can be claimed. (author)

  19. Fluctuations and Photons

    International Nuclear Information System (INIS)

    Gupta, Sourendu

    2007-01-01

    In this talk I discuss measures of fluctuations, especially those leading to the proof that the quark gluon plasma indeed contains quarks. I discuss the quark mass dependence of the critical end point of QCD. Then I discuss probes of the QCD critical point. Non-gaussian behaviour of event-to-event fluctuations of conserved quantum numbers is one such probe. Another is due to the coupling of fluctuations in baryon number and electrical charge, giving rise to long range random fluctuations of local charge density which relax slowly. These fluctuations can scatter photons, giving rise to critical opalescence

  20. Fluctuations and Photons

    Science.gov (United States)

    Gupta, Sourendu

    2007-02-01

    In this talk I discuss measures of fluctuations, especially those leading to the proof that the quark gluon plasma indeed contains quarks. I discuss the quark mass dependence of the critical end point of QCD. Then I discuss probes of the QCD critical point. Non-gaussian behaviour of event-to-event fluctuations of conserved quantum numbers is one such probe. Another is due to the coupling of fluctuations in baryon number and electrical charge, giving rise to long range random fluctuations of local charge density which relax slowly. These fluctuations can scatter photons, giving rise to critical opalescence.

  1. Fluctuations and Photons

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sourendu [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

    2007-02-15

    In this talk I discuss measures of fluctuations, especially those leading to the proof that the quark gluon plasma indeed contains quarks. I discuss the quark mass dependence of the critical end point of QCD. Then I discuss probes of the QCD critical point. Non-gaussian behaviour of event-to-event fluctuations of conserved quantum numbers is one such probe. Another is due to the coupling of fluctuations in baryon number and electrical charge, giving rise to long range random fluctuations of local charge density which relax slowly. These fluctuations can scatter photons, giving rise to critical opalescence.

  2. Delineating incoherent non-Markovian dynamics using quantum coherence

    Energy Technology Data Exchange (ETDEWEB)

    Chanda, Titas, E-mail: titaschanda@hri.res.in; Bhattacharya, Samyadeb, E-mail: samyadebbhattacharya@hri.res.in

    2016-03-15

    We introduce a method of characterization of non-Markovianity using coherence of a system interacting with the environment. We show that under the allowed incoherent operations, monotonicity of a valid coherence measure is affected due to non-Markovian features of the system–environment evolution. We also define a measure to quantify non-Markovianity of the underlying dynamics based on the non-monotonic behavior of the coherence measure. We investigate our proposed non-Markovianity marker in the behavior of dephasing and dissipative dynamics for one and two qubit cases. We also show that our proposed measure captures the back-flow of information from the environment to the system and compatible with well known distinguishability criteria of non-Markovianity.

  3. Color transparency in incoherent electroproduction of ρ mesons off nuclei

    International Nuclear Information System (INIS)

    Nemchik, J.; Kopeliovich, B. Z.; Potashnikova, I. K.

    2013-01-01

    Color transparency (CT) phenomena in elastic electroproduction of vector mesons off nuclei are usually infected by the onset of coherence length (CL) effects. However, at low energies corresponding to the CLAS experiment at Jefferson Lab (JLab), one can study practically the net CT effects, since CL is much shorter than the nuclear radius. We investigate various manifestations of CT effects using rigorous quantum mechanical approach based on the path integral technique. We include also the effects of ρ meson decay inside the nucleus leading to a rise of the nuclear suppression towards small values of Q 2 . Motivated by the last CLAS data we predict the A, Q 2 and l c dependence of nuclear transparency for ρ 0 mesons produced incoherently off nuclei. We also perform predictions for expected signal of CT corresponding to the planned JLab upgrade to 12 GeV electron beam.

  4. Incoherent beam combining based on the momentum SPGD algorithm

    Science.gov (United States)

    Yang, Guoqing; Liu, Lisheng; Jiang, Zhenhua; Guo, Jin; Wang, Tingfeng

    2018-05-01

    Incoherent beam combining (ICBC) technology is one of the most promising ways to achieve high-energy, near-diffraction laser output. In this paper, the momentum method is proposed as a modification of the stochastic parallel gradient descent (SPGD) algorithm. The momentum method can improve the speed of convergence of the combining system efficiently. The analytical method is employed to interpret the principle of the momentum method. Furthermore, the proposed algorithm is testified through simulations as well as experiments. The results of the simulations and the experiments show that the proposed algorithm not only accelerates the speed of the iteration, but also keeps the stability of the combining process. Therefore the feasibility of the proposed algorithm in the beam combining system is testified.

  5. Incoherent neutron scattering in acetanilide and three deuterated derivatives

    Science.gov (United States)

    Barthes, Mariette; Almairac, Robert; Sauvajol, Jean-Louis; Moret, Jacques; Currat, Roland; Dianoux, José

    1991-03-01

    Incoherent-neutron-scattering measurements of the vibrational density of states of acetanilide and three deuterated derivatives are presented. These data allow one to identify an intense maximum, assigned to the N-H out-of-plane bending mode. The data display the specific behavior of the methyl torsional modes: large isotopic shift and strong low-temperature intensity; confirm our previous inelastic-neutron-scattering studies, indicating no obvious anomalies in the range of frequency of the acoustic phonons. In addition, the data show the existence of thermally activated quasielastic scattering above 100 K, assigned to the random diffusive motion of the methyl protons. These results are discussed in the light of recent theoretical models proposed to explain the anomalous optical properties of this crystal.

  6. Incoherent Optical Frequency Domain Reflectometry for Distributed Thermal Sensing

    DEFF Research Database (Denmark)

    Karamehmedovic, Emir

    2006-01-01

    comprising a pump laser, optical filters, optical fibre and photo-detectors are presented. Limitations, trade-offs and optimisation processes are described for setups having different specifications with respect to range, resolution and accuracy. The analysis is conducted using computer simulation programs...... developed and implemented in Matlab. The computer model is calibrated and tested, and describes the entire system with high precision. Noise analysis and digital processing of the detected signal are discussed as well. An equation describing the standard deviation of the measured temperature is derived......This thesis reports the main results from an investigation of a fibre-optic distributed temperature sensor based on spontaneous Raman scattering. The technique used for spatial resolving is the incoherent optical frequency domain reflectometry, where a pump laser is sine modulated with a stepwise...

  7. Color transparency in incoherent electroproduction of {rho} mesons off nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Nemchik, J. [Institute of Experimental Physics SAS, Watsonova 47, 04001 Kosice, Slovakia and Czech Technical University, FNSPE, Brehova 7, 11519 Praque (Czech Republic); Kopeliovich, B. Z.; Potashnikova, I. K. [Departamento de Fisica y Centro de Estudios Subatomicos, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile)

    2013-04-15

    Color transparency (CT) phenomena in elastic electroproduction of vector mesons off nuclei are usually infected by the onset of coherence length (CL) effects. However, at low energies corresponding to the CLAS experiment at Jefferson Lab (JLab), one can study practically the net CT effects, since CL is much shorter than the nuclear radius. We investigate various manifestations of CT effects using rigorous quantum mechanical approach based on the path integral technique. We include also the effects of {rho} meson decay inside the nucleus leading to a rise of the nuclear suppression towards small values of Q{sup 2}. Motivated by the last CLAS data we predict the A, Q{sup 2} and l{sub c} dependence of nuclear transparency for {rho}{sup 0} mesons produced incoherently off nuclei. We also perform predictions for expected signal of CT corresponding to the planned JLab upgrade to 12 GeV electron beam.

  8. Radiation

    International Nuclear Information System (INIS)

    2013-01-01

    The chapter one presents the composition of matter and atomic theory; matter structure; transitions; origin of radiation; radioactivity; nuclear radiation; interactions in decay processes; radiation produced by the interaction of radiation with matter

  9. Electromagnetic radiation from a laser wakefield accelerator

    NARCIS (Netherlands)

    Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.

    2008-01-01

    Coherent and incoherent electromagnetic radiation emitted from a laser wakefield accelerator is calculated based on Lienard-Wiechert potentials. It is found that at wavelengths longer than the bunch length, the radiation is coherent. The coherent radiation, which typically lies in the infrared

  10. Statistical study of density fluctuations in the tore supra tokamak

    International Nuclear Information System (INIS)

    Devynck, P.; Fenzi, C.; Garbet, X.; Laviron, C.

    1998-03-01

    It is believed that the radial anomalous transport in tokamaks is caused by plasma turbulence. Using infra-red laser scattering technique on the Tore Supra tokamak, statistical properties of the density fluctuations are studied as a function of the scales in ohmic as well as additional heating regimes using the lower hybrid or the ion cyclotron frequencies. The probability distributions are compared to a Gaussian in order to estimate the role of intermittency which is found to be negligible. The temporal behaviour of the three-dimensional spectrum is thoroughly discussed; its multifractal character is reflected in the singularity spectrum. The autocorrelation coefficient as well as their long-time incoherence and statistical independence. We also put forward the existence of fluctuations transfer between two distinct but close wavenumbers. A rather clearer image is thus obtained about the way energy is transferred through the turbulent scales. (author)

  11. Coherence effects in radiative scattering

    International Nuclear Information System (INIS)

    Knoll, J.; Lenk, R.

    1993-03-01

    The bremsstrahl-production of photons in dense matter is reinvestigated using the example of an exactly solvable quantum mechanical model in one space dimension. Coherence phenomena between successive radiative scatterings among the constituents lead to a modification of the production cross section in the medium relative to the incoherent quasi-free prescription used in kinetic models. Analytic expressions for the correction factor have been derived comparing the quantum rates with the corresponding incoherent quasi-free rates. The result has implications for the kinetic description of all kinds of radiative processes in nucleus-nucleus collisions, both on the level of hadron and parton dynamics. (orig.)

  12. Single-shot self-interference incoherent digital holography using off-axis configuration.

    Science.gov (United States)

    Hong, Jisoo; Kim, Myung K

    2013-12-01

    We propose a single-shot incoherent holographic imaging technique that adopts self-interference incoherent digital holography (SIDH) with slight tilt of the plane mirror in the optical configuration. The limited temporal coherence length of the illumination leads the guide-star hologram of the proposed system to have a Gaussian envelope of elliptical ring shape. The observation shows that the reconstruction by cross correlation with the guide-star hologram achieves better quality than the usual propagation methods. Experimentally, we verify that the hologram and 3D reconstruction can be implemented incoherently with the proposed single-shot off-axis SIDH.

  13. Angular distribution of diffuse reflectance from incoherent multiple scattering in turbid media.

    Science.gov (United States)

    Gao, M; Huang, X; Yang, P; Kattawar, G W

    2013-08-20

    The angular distribution of diffuse reflection is elucidated with greater understanding by studying a homogeneous turbid medium. We modeled the medium as an infinite slab and studied the reflection dependence on the following three parameters: the incident direction, optical depth, and asymmetry factor. The diffuse reflection is produced by incoherent multiple scattering and is solved through radiative transfer theory. At large optical depths, the angular distribution of the diffuse reflection with small incident angles is similar to that of a Lambertian surface, but, with incident angles larger than 60°, the angular distributions have a prominent reflection peak around the specular reflection angle. These reflection peaks are found originating from the scattering within one transport mean free path in the top layer of the medium. The maximum reflection angles for different incident angles are analyzed and can characterize the structure of angular distributions for different asymmetry factors and optical depths. The properties of the angular distribution can be applied to more complex systems for a better understanding of diffuse reflection.

  14. Influence of intensity fluctuations on laser damage in optical materials

    International Nuclear Information System (INIS)

    Koldunov, M.F.; Manenkov, A.A.; Pocotilo, I.L.

    1995-01-01

    A study is reported of the influence of temporal fluctuations of laser radiation on the development of thermal explosion of absorbing inclusions and on the statistical properties of the laser induced damage in transparent dielectrics. A fluctuation time scale in which the fluctuations affect the thermal explosion of inclusions is established. An analysis is made of the conditions ensuring control of temporal fluctuations of laser radiation so as to eliminate their influence on the experimental statistical relationships governing laser damage associated with the distribution of absorbing inclusions in the bulk and on the surface of a sample

  15. Seeded Supercontinuum Generation - Modulation Instability Gain, Coherent and Incoherent Rogue Waves

    DEFF Research Database (Denmark)

    Sørensen, Simon Toft; Larsen, Casper; Møller, Uffe Visbech

    2012-01-01

    Deterministic supercontinuum can be generated by seeding the modulation instability-induced pulse break-up. We investigate the influence of the modulation instability gain on seeding and demonstrate the generation of coherent and incoherent rogue waves....

  16. Optical bistability via quantum interference from incoherent pumping and spontaneous emission

    International Nuclear Information System (INIS)

    Sahrai, M.; Asadpour, S.H.; Sadighi-Bonabi, R.

    2011-01-01

    We theoretically investigate the optical bistability (OB) in a V-type three-level atomic system confined in a unidirectional ring cavity via incoherent pumping field. It is shown that the threshold of optical bistability can be controlled by the rate of an incoherent pumping field and by interference mechanism arising from the spontaneous emission and incoherent pumping field. We demonstrate that the optical bistability converts to optical multi-stability (OM) by the quantum interference mechanism. - Highlights: → We modulate the optical bistability (OB) in a four-level N-type atomic system. → The threshold of optical bistability can be controlled by the quantum interferences. → OB converts to optical multi-stability (OM) by the quantum interferences. → We discuss the effect of an incoherent pumping field on reduction of OB threshold.

  17. "6"0Co-generated gamma radiation induced fluctuations on in vitro seed germination and callogenesis in Velvet bean (Mucunapruriens L.) seeds

    International Nuclear Information System (INIS)

    Misra, Pragati; Gupta, Ankit; Shukla, Pradeep Kumar

    2017-01-01

    Mucunapruriens exhibit many medicinal properties and almost every part of the plant contains metabolite of medicinal value. Irradiation treatments performed at in vitro culture has been also employed to increase genetic variability and mutants as a potential source of new commercial cultivars. Gamma rays are often used for developing plants varieties that are agriculturally and economically important and have high productivity potential with the minimum input. The callus induction frequency was in declined gradually with the increasing dose of gamma radiation. Gamma treated seeds developed greenish and fragile callus and also showed decreased weight as compare to control which was white greenish, compact and heavier. (author)

  18. Sub-Angstrom microscopy through incoherent imaging and image reconstruction

    International Nuclear Information System (INIS)

    Pennycook, S.J.; Jesson, D.E.; Chisholm, M.F.; Ferridge, A.G.; Seddon, M.J.

    1992-03-01

    Z-contrast scanning transmission electron microscopy (STEM) with a high-angle annular detector breaks the coherence of the imaging process, and provides an incoherent image of a crystal projection. Even in the presence of strong dynamical diffraction, the image can be accurately described as a convolution between an object function, sharply peaked at the projected atomic sites, and the probe intensity profile. Such an image can be inverted intuitively without the need for model structures, and therefore provides the important capability to reveal unanticipated interfacial arrangements. It represents a direct image of the crystal projection, revealing the location of the atomic columns and their relative high-angle scattering power. Since no phase is associated with a peak in the object function or the contrast transfer function, extension to higher resolution is also straightforward. Image restoration techniques such as maximum entropy, in conjunction with the 1.3 Angstrom probe anticipated for a 300 kV STEM, appear to provide a simple and robust route to the achievement of sub-Angstrom resolution electron microscopy

  19. An incoherent feedforward loop facilitates adaptive tuning of gene expression.

    Science.gov (United States)

    Hong, Jungeui; Brandt, Nathan; Abdul-Rahman, Farah; Yang, Ally; Hughes, Tim; Gresham, David

    2018-04-05

    We studied adaptive evolution of gene expression using long-term experimental evolution of Saccharomyces cerevisiae in ammonium-limited chemostats. We found repeated selection for non-synonymous variation in the DNA binding domain of the transcriptional activator, GAT1, which functions with the repressor, DAL80 in an incoherent type-1 feedforward loop (I1-FFL) to control expression of the high affinity ammonium transporter gene, MEP2. Missense mutations in the DNA binding domain of GAT1 reduce its binding to the GATAA consensus sequence. However, we show experimentally, and using mathematical modeling, that decreases in GAT1 binding result in increased expression of MEP2 as a consequence of properties of I1-FFLs. Our results show that I1-FFLs, one of the most commonly occurring network motifs in transcriptional networks, can facilitate adaptive tuning of gene expression through modulation of transcription factor binding affinities. Our findings highlight the importance of gene regulatory architectures in the evolution of gene expression. © 2018, Hong et al.

  20. Interference in the resonance fluorescence of two incoherently coupled transitions

    International Nuclear Information System (INIS)

    Kiffner, Martin; Evers, Joerg; Keitel, Christoph H.

    2006-01-01

    The fluorescence light emitted by a four-level system in J=1/2 to J=1/2 configuration driven by a monochromatic laser field and in an external magnetic field is studied. We show that the spectrum of resonance fluorescence emitted on the π transitions shows a signature of spontaneously generated interference effects. The degree of interference in the fluorescence spectrum can be controlled by means of the external magnetic field, provided that the Lande g factors of the excited and the ground state doublet are different. For a suitably chosen magnetic field strength, the relative weight of the Rayleigh line can be completely suppressed, even for low intensities of the coherent driving field. The incoherent fluorescence spectrum emitted on the π transitions exhibits a very narrow peak whose width and weight depend on the magnetic field strength. We demonstrate that the spectrum of resonance fluorescence emitted on the σ transitions shows an indirect signature of interference. A measurement of the relative peak heights in the spectrum from the σ transitions allows us to determine the branching ratio of the spontaneous decay of each excited state into the σ channel

  1. Higher derivative corrections to incoherent metallic transport in holography

    Energy Technology Data Exchange (ETDEWEB)

    Baggioli, Matteo [Institut de Física d’Altes Energies (IFAE), Universitat Autónoma de Barcelona,The Barcelona Institute of Science and Technology,Campus UAB, 08193 Bellaterra (Barcelona) (Spain); Crete Center for Theoretical Physics and I.P.P., Department of Physics, University of Crete,71003 Heraklion (Greece); Goutéraux, Blaise [Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Stanford Institute for Theoretical Physics, Department of Physics, Stanford University,Varian Laboratory of Physics, 382 Via Pueblo Mall, Stanford, CA 94305-4060 (United States); APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris,Sorbonne Paris Cité (UMR du CNRS 7164),Bâtiment Condorcet, 10, rue Alice Domon et Léonie Duquet, F-75205, Paris Cedex 13 (France); Kiritsis, Elias [APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris,Sorbonne Paris Cité (UMR du CNRS 7164),Bâtiment Condorcet, 10, rue Alice Domon et Léonie Duquet, F-75205, Paris Cedex 13 (France); Crete Center for Theoretical Physics and I.P.P., Department of Physics, University of Crete,71003 Heraklion (Greece); Crete Center for Quantum Complexity and Nanotechnology, University of Crete,71003 Heraklion (Greece); Li, Wei-Jia [Institute of Theoretical Physics, School of Physics and Optoelectronic Technology,Dalian University of Technology, 214 School of Physics,2 Linggong road, Ganjingzi District, Dalian 116024, Liaoning Province (China); Crete Center for Theoretical Physics and I.P.P., Department of Physics, University of Crete,71003 Heraklion (Greece)

    2017-03-31

    Transport in strongly-disordered, metallic systems is governed by diffusive processes. Based on quantum mechanics, it has been conjectured that these diffusivities obey a lower bound D/v{sup 2}≳ℏ/k{sub B}T, the saturation of which provides a mechanism for the T-linear resistivity of bad metals. This bound features a characteristic velocity v, which was later argued to be the butterfly velocity v{sub B}, based on holographic models of transport. This establishes a link between incoherent metallic transport, quantum chaos and Planckian timescales. Here we study higher derivative corrections to an effective holographic action of homogeneous disorder. The higher derivative terms involve only the charge and translation symmetry breaking sector. We show that they have a strong impact on the bound on charge diffusion D{sub c}/v{sub B}{sup 2}≳ℏ/k{sub B}T, by potentially making the coefficient of its right-hand side arbitrarily small. On the other hand, the bound on energy diffusion is not affected.

  2. Eikonal theory of the transition to phase incoherence

    International Nuclear Information System (INIS)

    Kaufman, A.N.; Rosengaus, E.

    1983-02-01

    When a monochromatic electromagnetic wave propagates through a nonuniform plasma (of n dimensions), its refraction may be studied in terms of its family of rays in 2n-dimensional phase space (k,x). These rays generate and n-dimensional surface. Imbedded in the phase space. The wave amplitude and phase are defined on this surface. As the rays twist and separate (from the dynamics of the ray Hamiltonian), the surface develops pleats and becomes convoluted. Projection of the surface onto x-space then yields a multivalued k(x). The local spectral density, as a function of k for given x, exhibits sharp spikes at these k(x), in the ray-optics limit. The next correction yields a finite width to these spikes. As the surface becomes more and more pppleated, these spectral peaks overlap; the spectrum changes qualitatively from a line spectrum to a continuous spectrum. Correspondingly, the two-point spatial correlation function loses its long-range order, as the correlation volume contracts. This phenomenon is what we call the transition to incoherence

  3. Repeated exposure to enhanced UV-B radiation in successive generations increases developmental instability (leaf fluctuating asymmetry) in a desert annual

    International Nuclear Information System (INIS)

    Midgley, G.F.; Wand, S.J.E.; Musil, C.F.

    1998-01-01

    Populations of the desert annual Dimorphotheca sinuata, derived from a common seed stock, were exposed concurrently over four successive generations to either ambient (representing no stratospheric ozone depletion) or elevated (representing 20% stratospheric ozone depletion) UV-B levels during their complete life cycle. Leaf fluctuating asymmetry (FA) was measured in populations of plants grown from seeds of selected generations which had experienced different UV-B exposure histories, and from seeds collected from a wild population of this species which grows in a naturally enhanced UV-B environment. These measured plants had been grown in a greenhouse under essentially UV-B-free conditions. Leaf FA was significantly increased by greater numbers of enhanced UV-B exposures in the parentage of the seed. There was a linear to exponential dose–response relationship between number of UV-B exposure iterations in seed parentage and leaf FA, suggesting that damage to DNA caused by UV-B exposure during plant development may not be fully repaired, and thus be inherited by offspring and accumulated over successive generations in this species. Leaf FA of plants grown from seed from the wild population was not significantly greater than that of control plants whose parentage experienced only ambient UV-B exposures, although this negative result may have been due to low sampling intensity and measurement resolution, and the relatively low UV-B enhancement experienced by the wild population. We conclude that leaf FA may constitute a relatively sensitive yet inexpensive means of quantifying UV-B damage to plants. (author)

  4. Superconductivity and spin fluctuations

    International Nuclear Information System (INIS)

    Scalapino, D.J.

    1999-01-01

    The organizers of the Memorial Session for Herman Rietschel asked that the author review some of the history of the interplay of superconductivity and spin fluctuations. Initially, Berk and Schrieffer showed how paramagnon spin fluctuations could suppress superconductivity in nearly-ferromagnetic materials. Following this, Rietschel and various co-workers wrote a number of papers in which they investigated the role of spin fluctuations in reducing the Tc of various electron-phonon superconductors. Paramagnon spin fluctuations are also believed to provide the p-wave pairing mechanism responsible for the superfluid phases of 3 He. More recently, antiferromagnetic spin fluctuations have been proposed as the mechanism for d-wave pairing in the heavy-fermion superconductors and in some organic materials as well as possibly the high-Tc cuprates. Here the author will review some of this early history and discuss some of the things he has learned more recently from numerical simulations

  5. Coherent vs Incoherent Emission from Semiconductor Structures after Resonant Femtosecond Excitation

    Science.gov (United States)

    Gurioli, Massimo; Bogani, Franco; Ceccherini, Simone; Colocci, Marcello

    1997-04-01

    We show that an interferometric correlation measurement with fs time resolution provides an unambiguous discrimination between coherent and incoherent emission after resonant femtosecond excitation. The experiment directly probes the most important difference between the two emissions, that is, the phase correlation with the excitation pulse. The comparison with cw frequency resolved measurements demonstrates that the relationship between coherent and incoherent emission is similar under femtosecond and steady-state excitation.

  6. Nonlinear dispersion-based incoherent photonic processing for microwave pulse generation with full reconfigurability.

    Science.gov (United States)

    Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2012-03-12

    A novel all-optical technique based on the incoherent processing of optical signals using high-order dispersive elements is analyzed for microwave arbitrary pulse generation. We show an approach which allows a full reconfigurability of a pulse in terms of chirp, envelope and central frequency by the proper control of the second-order dispersion and the incoherent optical source power distribution, achieving large values of time-bandwidth product.

  7. Experimental photonic generation of chirped pulses using nonlinear dispersion-based incoherent processing.

    Science.gov (United States)

    Rius, Manuel; Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2015-05-18

    We experimentally demonstrate, for the first time, a chirped microwave pulses generator based on the processing of an incoherent optical signal by means of a nonlinear dispersive element. Different capabilities have been demonstrated such as the control of the time-bandwidth product and the frequency tuning increasing the flexibility of the generated waveform compared to coherent techniques. Moreover, the use of differential detection improves considerably the limitation over the signal-to-noise ratio related to incoherent processing.

  8. Fluctuations and structure of amphiphilic films

    International Nuclear Information System (INIS)

    Gourier, CH.

    1996-01-01

    This thesis is divided in three parts.The first part exposes in a theoretical point of view, how the fluctuations spectrum of an amphiphilic film is governed by its properties and its bidimensional characteristics.The measurements of fluctuations spectra of an interface are accessible with the measurement of intensity that interface diffuses out of the specular angle, we present in the second chapter the principles of the X rays diffusion by a real interface and see how the diffuse diffusion experiments allow to determine the fluctuations spectrum of an amphiphilic film. The second part is devoted to the different experimental techniques that have allowed to realize the study of fluctuation as well as the structural study.The third part is devoted to experimental results concerning the measurements of fluctuations spectra and to the study of the structure of amphiphilic films. We show that it is possible by using an intense source of X rays (ESRF: European Synchrotron Radiation Facility) to measure the water and amphiphilic films fluctuations spectra until molecular scales. The last chapter is devoted to the structural study and film fluctuations made of di-acetylenic molecules. (N.C.)

  9. Optical image encryption method based on incoherent imaging and polarized light encoding

    Science.gov (United States)

    Wang, Q.; Xiong, D.; Alfalou, A.; Brosseau, C.

    2018-05-01

    We propose an incoherent encoding system for image encryption based on a polarized encoding method combined with an incoherent imaging. Incoherent imaging is the core component of this proposal, in which the incoherent point-spread function (PSF) of the imaging system serves as the main key to encode the input intensity distribution thanks to a convolution operation. An array of retarders and polarizers is placed on the input plane of the imaging structure to encrypt the polarized state of light based on Mueller polarization calculus. The proposal makes full use of randomness of polarization parameters and incoherent PSF so that a multidimensional key space is generated to deal with illegal attacks. Mueller polarization calculus and incoherent illumination of imaging structure ensure that only intensity information is manipulated. Another key advantage is that complicated processing and recording related to a complex-valued signal are avoided. The encoded information is just an intensity distribution, which is advantageous for data storage and transition because information expansion accompanying conventional encryption methods is also avoided. The decryption procedure can be performed digitally or using optoelectronic devices. Numerical simulation tests demonstrate the validity of the proposed scheme.

  10. Hadronic Correlations and Fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Volker

    2008-10-09

    We will provide a review of some of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. We will discuss Lattice QCD results on fluctuations and correlations and will put them into context with observables which have been measured in heavy-ion collisions. Special attention will be given to the QCD critical point and the first order co-existence region, and we will discuss how the measurement of fluctuations and correlations can help in an experimental search for non-trivial structures in the QCD phase diagram.

  11. Quantum fluctuations and inflation

    International Nuclear Information System (INIS)

    Bardeen, J.M.; Bublik, G.J.

    1986-05-01

    We study the effect of quantum fluctuations on the roll-down rate of the inflation field in a semiclassical approximation; this is done by treating the inflation field as a classical random field. The quantum fluctuations are simulated by a noise term in the equation of motion. We consider two different inflationary scenarios (new and chaotic inflation) and find that the roll-down rate of the median value of the inflation field is increased by the quantum fluctuations. Non-linear effects may become important in the later stages of the inflationary regime. 8 refs., 2 figs

  12. Quantum fluctuations and inflation

    International Nuclear Information System (INIS)

    Bardeen, J.M.; Bublik, G.J.

    1987-01-01

    The authors study the effect of quantum fluctuations on the roll-down rate of the inflation field in a semiclassical approximation; this is done by treating the inflation field as a classical random field. The quantum fluctuations are simulated by a noise term in the equation of motion. Two different inflationary scenarios (new and chaotic inflation) are considered and it is found that the roll-down rate of the median value of the inflation field is increased by the quantum fluctuations. Non-linear effects may become important in the later stages of the inflationary regime. (author)

  13. Fluorescence fluctuation spectroscopy (FFS)

    CERN Document Server

    Tetin, Sergey

    2012-01-01

    This new volume of Methods in Enzymology continues the legacy of this premier serial with quality chapters authored by leaders in the field. This volume covers fluorescence fluctuation spectroscopy and includes chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells. Continues the legacy of this premier serial with quality chapters authored by leaders in the field Covers fluorescence fluctuation spectroscopy Contains chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells.

  14. Fully Quantum Fluctuation Theorems

    Science.gov (United States)

    Åberg, Johan

    2018-02-01

    Systems that are driven out of thermal equilibrium typically dissipate random quantities of energy on microscopic scales. Crooks fluctuation theorem relates the distribution of these random work costs to the corresponding distribution for the reverse process. By an analysis that explicitly incorporates the energy reservoir that donates the energy and the control system that implements the dynamic, we obtain a quantum generalization of Crooks theorem that not only includes the energy changes in the reservoir but also the full description of its evolution, including coherences. Moreover, this approach opens up the possibility for generalizations of the concept of fluctuation relations. Here, we introduce "conditional" fluctuation relations that are applicable to nonequilibrium systems, as well as approximate fluctuation relations that allow for the analysis of autonomous evolution generated by global time-independent Hamiltonians. We furthermore extend these notions to Markovian master equations, implicitly modeling the influence of the heat bath.

  15. From coherent to incoherent mismatched interfaces: A generalized continuum formulation of surface stresses

    Science.gov (United States)

    Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

    2014-12-01

    The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. The coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent and incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.

  16. Universal mesoscopic conductance fluctuations

    International Nuclear Information System (INIS)

    Evangelou, S.N.

    1992-01-01

    The theory of conductance fluctuations in disordered metallic systems with size large compared to the mean free path of the electron but small compared to localization length is considered. It is demonstrates that fluctuations have an universal character and are due to repulsion between levels and spectral rigidity. The basic fluctuation measures for the energy spectrum in the mesoscopic regime of disordered systems are consistent with the Gaussian random matrix ensemble predictions. Although our disordered electron random matrix ensemble does not belong to the Gaussian ensemble the two ensembles turn out to be essentially similar. The level repulsion and the spectral rigidity found in nuclear spectra should also be observed in the metallic regime of Anderson localization. 7 refs. (orig.)

  17. Spin fluctuations and the

    Directory of Open Access Journals (Sweden)

    V.M. Loktev

    2008-09-01

    Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.

  18. Investigations of homologous disaccharides by elastic incoherent neutron scattering and wavelet multiresolution analysis

    Energy Technology Data Exchange (ETDEWEB)

    Magazù, S.; Migliardo, F. [Dipartimento di Fisica e di Scienze della Terra dell’, Università degli Studi di Messina, Viale F. S. D’Alcontres 31, 98166 Messina (Italy); Vertessy, B.G. [Institute of Enzymology, Hungarian Academy of Science, Budapest (Hungary); Caccamo, M.T., E-mail: maccamo@unime.it [Dipartimento di Fisica e di Scienze della Terra dell’, Università degli Studi di Messina, Viale F. S. D’Alcontres 31, 98166 Messina (Italy)

    2013-10-16

    Highlights: • Innovative multiresolution wavelet analysis of elastic incoherent neutron scattering. • Elastic Incoherent Neutron Scattering measurements on homologues disaccharides. • EINS wavevector analysis. • EINS temperature analysis. - Abstract: In the present paper the results of a wavevector and thermal analysis of Elastic Incoherent Neutron Scattering (EINS) data collected on water mixtures of three homologous disaccharides through a wavelet approach are reported. The wavelet analysis allows to compare both the spatial properties of the three systems in the wavevector range of Q = 0.27 Å{sup −1} ÷ 4.27 Å{sup −1}. It emerges that, differently from previous analyses, for trehalose the scalograms are constantly lower and sharper in respect to maltose and sucrose, giving rise to a global spectral density along the wavevector range markedly less extended. As far as the thermal analysis is concerned, the global scattered intensity profiles suggest a higher thermal restrain of trehalose in respect to the other two homologous disaccharides.

  19. Fluctuations and structure of amphiphilic films; Fluctuations et structure de films d`amphiphiles

    Energy Technology Data Exchange (ETDEWEB)

    Gourier, CH

    1996-07-01

    This thesis is divided in three parts.The first part exposes in a theoretical point of view, how the fluctuations spectrum of an amphiphilic film is governed by its properties and its bidimensional characteristics.The measurements of fluctuations spectra of an interface are accessible with the measurement of intensity that interface diffuses out of the specular angle, we present in the second chapter the principles of the X rays diffusion by a real interface and see how the diffuse diffusion experiments allow to determine the fluctuations spectrum of an amphiphilic film. The second part is devoted to the different experimental techniques that have allowed to realize the study of fluctuation as well as the structural study.The third part is devoted to experimental results concerning the measurements of fluctuations spectra and to the study of the structure of amphiphilic films. We show that it is possible by using an intense source of X rays (ESRF: European Synchrotron Radiation Facility) to measure the water and amphiphilic films fluctuations spectra until molecular scales. The last chapter is devoted to the structural study and film fluctuations made of di-acetylenic molecules. (N.C.)

  20. The fluctuating gap model

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Xiaobin

    2011-01-15

    The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above T{sub c} in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the

  1. The fluctuating gap model

    International Nuclear Information System (INIS)

    Cao, Xiaobin

    2011-01-01

    The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above T c in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the quasi

  2. Proposal for the development of ICNIRP guidelines on limits for optical radiation exposure

    Energy Technology Data Exchange (ETDEWEB)

    Siekmann, H. [Berufsgenossenschaftliches Institut fuer Arbeitsschutz - FIA, Sankt Augustin (Germany); Reidenbach, H.D. [Fachhochschule Koeln (Germany)

    2004-07-01

    Guidelines on limits of exposure to incoherent ultraviolet radiation, to incoherent visible and infrared radiation and to laser radiation have been published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). These guidelines are accepted globally and form the basis for risk assessment procedures for optical radiation in many countries. With the appearance of new scientific cognition the ICNIRP guidelines will be revised from time to time. A revision may also concern more formal aspects. Some proposals for the development of the ICNIRP limit value recommendations for optical radiation exposures follow. (orig.)

  3. Todd Berliner. Hollywood Incoherent. Narration in Seventies Cinema.

    Directory of Open Access Journals (Sweden)

    Pascal Lefèvre

    2010-12-01

    Full Text Available

    Todd Berliner. Hollywood Incoherent. Narration in Seventies Cinema.

    Austin: University of Texas Press, 2010.

    ISBN-10: 0292722796

    ISBN-13: 978-0292722798

     

     

  4. Controlling the light propagation in one-dimensional photonic crystal via incoherent pump and interdot tunneling

    Science.gov (United States)

    Abbasabadi, Majid; Sahrai, Mostafa

    2018-01-01

    We investigated the propagation of an electromagnetic pulse through a one-dimensional photonic crystal doped with quantum-dot (QD) molecules in a defect layer. The QD molecules behave as a three-level quantum system and are driven by a coherent probe laser field and an incoherent pump field. No coherent coupling laser fields were introduced, and the coherence was created by the interdot tunnel effect. Further studied was the effect of tunneling and incoherent pumping on the group velocity of the transmitted and reflected probe pulse.

  5. Ultrafast Dephasing and Incoherent Light Photon Echoes in Organic Amorphous Systems

    Science.gov (United States)

    Yano, Ryuzi; Matsumoto, Yoshinori; Tani, Toshiro; Nakatsuka, Hiroki

    1989-10-01

    Incoherent light photon echoes were observed in organic amorphous systems (cresyl violet in polyvinyl alcohol and 1,4-dihydroxyanthraquinone in polymethacrylic acid) by using temporally-incoherent nanosecond laser pulses. It was found that an echo decay curve of an organic amorphous system is composed of a sharp peak which decays very rapidly and a slowly decaying wing at the tail. We show that the persistent hole burning (PHB) spectra were reproduced by the Fourier-cosine transforms of the echo decay curves. We claim that in general, we must take into account the multi-level feature of the system in order to explain ultrafast dephasing at very low temperatures.

  6. Incoherently Coupled Grey-Grey Spatial Soliton Pairs in Biased Two-Photon Photovoltaic Photorefractive Crystals

    International Nuclear Information System (INIS)

    Su Yanli; Jiang Qichang; Ji Xuanmang

    2010-01-01

    The incoherently coupled grey-grey screening-photovoltaic spatial soliton pairs are predicted in biased two-photon photovoltaic photorefractive crystals under steady-state conditions. These grey-grey screening-photovoltaic soliton pairs can be established provided that the incident beams have the same polarization, wavelength, and are mutually incoherent. The grey-grey screening-photovoltaic soliton pairs can be considered as the united form of grey-grey screening soliton pairs and open or closed-circuit grey-grey photovoltaic soliton pairs. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  7. Fluctuating Asymmetry and Intelligence

    Science.gov (United States)

    Bates, Timothy C.

    2007-01-01

    The general factor of mental ability ("g") may reflect general biological fitness. If so, "g"-loaded measures such as Raven's progressive matrices should be related to morphological measures of fitness such as fluctuating asymmetry (FA: left-right asymmetry of a set of typically left-right symmetrical body traits such as finger…

  8. Incoherent-scatter computed tomography with monochromatic synchrotron x ray: feasibility of multi-CT imaging system for simultaneous measurement-of fluorescent and incoherent scatter x rays

    Science.gov (United States)

    Yuasa, T.; Akiba, M.; Takeda, T.; Kazama, M.; Hoshino, A.; Watanabe, Y.; Hyodo, K.; Dilmanian, F. A.; Akatsuka, T.; Itai, Y.

    1997-10-01

    We describe a new system of incoherent scatter computed tomography (ISCT) using monochromatic synchrotron X rays, and we discuss its potential to be used in in vivo imaging for medical use. The system operates on the basis of computed tomography (CT) of the first generation. The reconstruction method for ISCT uses the least squares method with singular value decomposition. The research was carried out at the BLNE-5A bending magnet beam line of the Tristan Accumulation Ring in KEK, Japan. An acrylic cylindrical phantom of 20-mm diameter containing a cross-shaped channel was imaged. The channel was filled with a diluted iodine solution with a concentration of 200 /spl mu/gI/ml. Spectra obtained with the system's high purity germanium (HPGe) detector separated the incoherent X-ray line from the other notable peaks, i.e., the iK/sub /spl alpha// and K/sub /spl beta/1/ X-ray fluorescent lines and the coherent scattering peak. CT images were reconstructed from projections generated by integrating the counts In the energy window centering around the incoherent scattering peak and whose width was approximately 2 keV. The reconstruction routine employed an X-ray attenuation correction algorithm. The resulting image showed more homogeneity than one without the attenuation correction.

  9. Incoherent SSI Analysis of Reactor Building using 2007 Hard-Rock Coherency Model

    International Nuclear Information System (INIS)

    Kang, Joo-Hyung; Lee, Sang-Hoon

    2008-01-01

    Many strong earthquake recordings show the response motions at building foundations to be less intense than the corresponding free-field motions. To account for these phenomena, the concept of spatial variation, or wave incoherence was introduced. Several approaches for its application to practical analysis and design as part of soil-structure interaction (SSI) effect have been developed. However, conventional wave incoherency models didn't reflect the characteristics of earthquake data from hard-rock site, and their application to the practical nuclear structures on the hard-rock sites was not justified sufficiently. This paper is focused on the response impact of hard-rock coherency model proposed in 2007 on the incoherent SSI analysis results of nuclear power plant (NPP) structure. A typical reactor building of pressurized water reactor (PWR) type NPP is modeled classified into surface and embedded foundations. The model is also assumed to be located on medium-hard rock and hard-rock sites. The SSI analysis results are obtained and compared in case of coherent and incoherent input motions. The structural responses considering rocking and torsion effects are also investigated

  10. Time-stretch microscopy based on time-wavelength sequence reconstruction from wideband incoherent source

    International Nuclear Information System (INIS)

    Zhang, Chi; Xu, Yiqing; Wei, Xiaoming; Tsia, Kevin K.; Wong, Kenneth K. Y.

    2014-01-01

    Time-stretch microscopy has emerged as an ultrafast optical imaging concept offering the unprecedented combination of the imaging speed and sensitivity. However, dedicated wideband and coherence optical pulse source with high shot-to-shot stability has been mandated for time-wavelength mapping—the enabling process for ultrahigh speed wavelength-encoded image retrieval. From the practical point of view, exploiting methods to relax the stringent requirements (e.g., temporal stability and coherence) for the source of time-stretch microscopy is thus of great value. In this paper, we demonstrated time-stretch microscopy by reconstructing the time-wavelength mapping sequence from a wideband incoherent source. Utilizing the time-lens focusing mechanism mediated by a narrow-band pulse source, this approach allows generation of a wideband incoherent source, with the spectral efficiency enhanced by a factor of 18. As a proof-of-principle demonstration, time-stretch imaging with the scan rate as high as MHz and diffraction-limited resolution is achieved based on the wideband incoherent source. We note that the concept of time-wavelength sequence reconstruction from wideband incoherent source can also be generalized to any high-speed optical real-time measurements, where wavelength is acted as the information carrier

  11. New neutron-based isotopic analytical methods; An explorative study of resonance capture and incoherent scattering

    NARCIS (Netherlands)

    Perego, R.C.

    2004-01-01

    Two novel neutron-based analytical techniques have been treated in this thesis, Neutron Resonance Capture Analysis (NRCA), employing a pulsed neutron source, and Neutron Incoherent Scattering (NIS), making use of a cold neutron source. With the NRCA method isotopes are identified by the

  12. Incoherent neutron-scattering determination of hydrogen content : Theory and modeling

    NARCIS (Netherlands)

    Perego, R.C.; Blaauw, M.

    2005-01-01

    Hydrogen concentrations of 0 up to 350?mg/kg in a titanium alloy have been determined at National Institute of Standards and Technology (NIST) with neutron incoherent scattering (NIS) and with cold neutron prompt gamma activation analysis. The latter is a well-established technique, while the former

  13. Coherent laser phase retrieval in the presence of measurement imperfections and incoherent light

    DEFF Research Database (Denmark)

    Hansen, Anders Kragh

    2017-01-01

    -plane Gerchberg–Saxton algorithm and demonstrate that it is highly successful at extracting the intensity profile and wavefront of the spatially coherent part of the light from various lasers, including tapered laser diodes, at a very high fidelity despite the presence of incoherent light and noise....

  14. Optical sectioning using a digital Fresnel incoherent-holography-based confocal imaging system

    Science.gov (United States)

    Kelner, Roy; Katz, Barak; Rosen, Joseph

    2015-01-01

    We propose a new type of confocal microscope using Fresnel incoherent correlation holography (FINCH). Presented here is a confocal configuration of FINCH using a phase pinhole and point illumination that is able to suppress out-of-focus information from the recorded hologram and hence combine the super-resolution capabilities of FINCH with the sectioning capabilities of confocal microscopy. PMID:26413560

  15. Optical sectioning using a digital Fresnel incoherent-holography-based confocal imaging system

    OpenAIRE

    Kelner, Roy; Katz, Barak; Rosen, Joseph

    2014-01-01

    We propose a new type of confocal microscope using Fresnel incoherent correlation holography (FINCH). Presented here is a confocal configuration of FINCH using a phase pinhole and point illumination that is able to suppress out-of-focus information from the recorded hologram and hence combine the super-resolution capabilities of FINCH with the sectioning capabilities of confocal microscopy.

  16. Measurements of integral cross-sections of incoherent interactions of photons with L-shell electrons

    Energy Technology Data Exchange (ETDEWEB)

    Verma, S L; Allawadhi, K L; Sood, B S [Punjabi Univ., Patiala (India). Nuclear Science Labs.

    1983-05-21

    Integral cross-sections of incoherent interactions of 662 and 1250 keV gamma-rays with L-shell electrons of different elements with 74<=Z<=92 have been measured. The experimental results, when interpreted in terms of photoelectric and Compton interaction cross-sections, are found to agree with theory.

  17. Measurement of integral cross-sections of incoherent interactions of photons with K-shell electrons

    Energy Technology Data Exchange (ETDEWEB)

    Verma, S L; Allawadhi, K L; Sood, B S [Punjabi Univ., Patiala (India). Dept. of Physics. Nuclear Science Labs.

    1981-06-01

    Integral cross-sections of incoherent interactions of 145, 279, 662 and 1250 keV gamma-rays with K-shell electrons of thirty-one different elements with 26 <= Z <= 92 have been measured. The results are interpreted in terms of the photoelectric and Compton interactions and are found to agree with theory.

  18. Velocity-Autocorrelation Function in Liquids, Deduced from Neutron Incoherent Scattering Results

    DEFF Research Database (Denmark)

    Carneiro, Kim

    1976-01-01

    The Fourier transform p(ω) of the velocity-autocorrelation function is derived from neutron incoherent scattering results, obtained from the two liquids Ar and H2. The quality and significance of the results are discussed with special emphasis on the long-time t-3/2 tail, found in computer simula...

  19. Determination of the thermospheric neutral wind from incoherent scatter radar measurements

    International Nuclear Information System (INIS)

    Haeggstroem, I.; Murdin, J.; Rees, D.

    1984-11-01

    Measurements made by the EISCAT UHF incoherent scatter radar are used to derive thermospheric winds. The derived wind is compared to Fabry-Perot interferometer measurements of the neutral wind made simultaneously. The uncertainties in the radar derived wind are discussed. (author)

  20. Incoherent Scatter Radar Studies of Daytime Plasma Lines

    Science.gov (United States)

    Djuth, Frank T.; Carlson, Herbert C.; Zhang, Liwei D.

    2018-03-01

    First results from wideband (electron phase energies of 5-51 eV), high-resolution (0.1 eV) spectral measurements of photoelectron-enhanced plasma lines made with the 430 MHz radar at Arecibo Observatory are presented. In the F region, photoelectrons produced by solar EUV line emissions (He II and Mg IX) give rise to plasma line spectral peaks/valleys. These and other structures occur within an enhancement zone extending from electron phase energies of 14-27 eV in both the bottomside and topside ionosphere. However, photoelectron-thermal electron Coulomb energy losses can lead to a broadened spectral structure with no resolved peaks in the topside ionosphere. The plasma line energy spectra obtained in the enhancement zone exhibit a unique relation in that phase energy is dependent on pitch angle; this relation does not exist in any other part of the energy spectrum. Moreover, large fluctuations in the difference frequency between the upshifted and downshifted plasma lines are evident in the 14-27 eV energy interval. At high phase energies near 51 eV the absolute intensities of photoelectron-excited Langmuir waves are much larger than those predicted by existing theory. The new measurements call for a revision/improvement of plasma line theory in several key areas.

  1. Fluctuations in quantum devices

    Directory of Open Access Journals (Sweden)

    H.Haken

    2004-01-01

    Full Text Available Logical gates can be formalized by Boolean algebra whose elementary operations can be realized by devices that employ the interactions of macroscopic numbers of elementary excitations such as electrons, holes, photons etc. With increasing miniaturization to the nano scale and below, quantum fluctuations become important and can no longer be ignored. Based on Heisenberg equations of motion for the creation and annihilation operators of elementary excitations, I determine the noise sources of composite quantum systems.

  2. Significance of quantum fluctuations in roentgen imaging

    Energy Technology Data Exchange (ETDEWEB)

    Strid, K G [Sahlgrenska Sjukhuset, Goeteborg (Sweden)

    1980-01-01

    Quantum fluctuations in the roentgen radiation relief are analysed mathematically. The intrinsic signal-to-noise ratio of the radiation relief for a given object contrast is proportional to the square root of the number of photons contributing to the image of a characteristic detail in the object. In the presence of secondary radiation the signal-to-noise ratio is impaired, since the fluctuations of secondary radiation increase the noise of the radiation relief. By efficient secondary screening, the quality of the relief can be partially recovered. With a dynamically limited recording device, i.e. a film-screen combination, increased detection speed in conjunction with improved secondary screening will either result in unchanged image quality with the gain of an object-dose reduction or provide improved imaging at an unchanged dose value. As regards the relation between contrast resolution and spatial resolution, the dose required to barely demonstrate an object detail of given geometry and composition is found to vary inversely with the fourth power of the linear size of the detail. It is also concluded that recording and secondary-screening devices should always be considered together as far as recording quality is concerned.

  3. Radiations

    International Nuclear Information System (INIS)

    Pujol Mora, J.

    1999-01-01

    The exposition to ionizing radiations is a constant fact in the life of the human being and its utilization as diagnostic and therapeutic method is generalized. However, it is notorious how as years go on, the fear to the ionizing radiation seems to persist too, and this fact is not limited to the common individual, but to the technical personnel and professional personnel that labors with them same. (S. Grainger) [es

  4. Radiation

    International Nuclear Information System (INIS)

    Davidson, J.H.

    1986-01-01

    The basic facts about radiation are explained, along with some simple and natural ways of combating its ill-effects, based on ancient healing wisdom as well as the latest biochemical and technological research. Details are also given of the diet that saved thousands of lives in Nagasaki after the Atomic bomb attack. Special comment is made on the use of radiation for food processing. (U.K.)

  5. Hawking radiation

    Science.gov (United States)

    Parentani, Renaud; Spindel, Philippe

    2011-12-01

    Hawking radiation is the thermal radiation predicted to be spontaneously emitted by black holes. It arises from the steady conversion of quantum vacuum fluctuations into pairs of particles, one of which escaping at infinity while the other is trapped inside the black hole horizon. It is named after the physicist Stephen Hawking who derived its existence in 1974. This radiation reduces the mass of black holes and is therefore also known as black hole evaporation.

  6. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, É lisabeth; Hinch, John

    2011-01-01

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations

  7. Radiation

    International Nuclear Information System (INIS)

    Winther, J.F.; Ulbak, K.; Dreyer, L.; Pukkala, E.; Oesterlind, A.

    1997-01-01

    Exposure to solar and ionizing radiation increases the risk for cancer in humans. Some 5% of solar radiation is within the ultraviolet spectrum and may cause both malignant melanoma and non-melanocytic skin cancer; the latter is regarded as a benign disease and is accordingly not included in our estimation of avoidable cancers. Under the assumption that the rate of occurrence of malignant melanoma of the buttocks of both men and women and of the scalp of women would apply to all parts of the body in people completely unexposed to solar radiation, it was estimated that approximately 95% of all malignant melanomas arising in the Nordic populations around the year 2000 will be due to exposure to natural ultraviolet radiation, equivalent to an annual number of about 4700 cases, with 2100 in men and 2600 in women, or some 4% of all cancers notified. Exposure to ionizing radiation in the Nordic countries occurs at an average effective dose per capita per year of about 3 mSv (Iceland, 1.1 mSv) from natural sources, and about 1 mSv from man-made sources. While the natural sources are primarily radon in indoor air, natural radionuclides in food, cosmic radiation and gamma radiation from soil and building materials, the man-made sources are dominated by the diagnostic and therapeutic use of ionizing radiation. On the basis of measured levels of radon in Nordic dwellings and associated risk estimates for lung cancer derived from well-conducted epidemiological studies, we estimated that about 180 cases of lung cancer (1% of all lung cancer cases) per year could be avoided in the Nordic countries around the year 2000 if indoor exposure to radon were eliminated, and that an additional 720 cases (6%) could be avoided annually if either radon or tobacco smoking were eliminated. Similarly, it was estimated that the exposure of the Nordic populations to natural sources of ionizing radiation other than radon and to medical sources will each give rise to an annual total of 2120

  8. Fluctuations in Schottky barrier heights

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1984-01-01

    A double Schottky barrier is often formed at the grain boundary in polycrystalline semiconductors. The barrier height is shown to fluctuate in value due to the random nature of the impurity positions. The magnitude of the fluctuations is 0.1 eV, and the fluctuations cause the barrier height measured by capacitance to differ from the one measured by electrical conductivity

  9. The effect of the precipitation of coherent and incoherent precipitates on the ductility and toughness of high-strength steel

    International Nuclear Information System (INIS)

    Hamano, R.

    1993-01-01

    The effect of the coexistence of coherent and incoherent precipitates, such as M 2 C and NiAl, on the ductility and plane strain fracture toughness of 5 wt pct Ni-2 wt pct Al-based high-strength steels was studied. In order to disperse coherent and incoherent precipitates, the heat treatments were carried out as follows: (a) austenitizing at 1373 K, (b) tempering at 1023 or 923 K for dispersing the incoherent precipitates of M 2 C and NiAl, and then (c) aging at 843 K for 2.4 ks to disperse the coherent precipitate of NiAl into the matrix, which contains incoherent precipitates, such as M 2 C and NiAl. The results were obtained as follows: (a) when the strengthening precipitates consist of coherent ones, such as M 2 C and/or NiAl, the ductility and toughness are extremely low, and (b) when the strengthening precipitates consist of coherent and incoherent precipitates, such as M 2 C and NiAl, the ductility and fracture toughness significantly increase with no loss in strength. It is shown that the coexistence of coherent and incoherent precipitates increases homogeneous deformation, thus preventing local strain concentration and early cleavage cracking. Accordingly, the actions of coherent precipitates in strengthening the matrix and of incoherent precipitates in promoting, homogeneous deformation can be expected to increase both the strength and toughness of the material

  10. Strain fluctuations and elastic constants

    Energy Technology Data Exchange (ETDEWEB)

    Parrinello, M.; Rahman, A.

    1982-03-01

    It is shown that the elastic strain fluctuations are a direct measure of elastic compliances in a general anisotropic medium; depending on the ensemble in which the fluctuation is measured either the isothermal or the adiabatic compliances are obtained. These fluctuations can now be calculated in a constant enthalpy and pressure, and hence, constant entropy, ensemble due to recent develpments in the molecular dynamics techniques. A calculation for a Ni single crystal under uniform uniaxial 100 tensile or compressive load is presented as an illustration of the relationships derived between various strain fluctuations and the elastic modulii. The Born stability criteria and the behavior of strain fluctuations are shown to be related.

  11. Gambling with Superconducting Fluctuations

    Science.gov (United States)

    Foltyn, Marek; Zgirski, Maciej

    2015-08-01

    Josephson junctions and superconducting nanowires, when biased close to superconducting critical current, can switch to a nonzero voltage state by thermal or quantum fluctuations. The process is understood as an escape of a Brownian particle from a metastable state. Since this effect is fully stochastic, we propose to use it for generating random numbers. We present protocol for obtaining random numbers and test the experimentally harvested data for their fidelity. Our work is prerequisite for using the Josephson junction as a tool for stochastic (probabilistic) determination of physical parameters such as magnetic flux, temperature, and current.

  12. Fluctuations in the hadronization

    International Nuclear Information System (INIS)

    Bozek, P.; Ploszajaczak, M.

    1992-01-01

    The multiscaling in the fluctuations of the multiparticle distributions at small scales is studied. Similarly to the multiscaling effect, recently found in multifractal models, the dependence of the intermittency patterns on the low density cut-off in the cascade is analyzed. The effect changes the scaling behaviour and leads to stronger dependence of the scaled factorial moments on the resolution than the power law. This could be an explanation of the behaviour observed recently in the experimental 3-dimensional data. The multiscaling analysis allows to restore the universality in the processes with different cut-offs and could be used in the analysis of the experimental data. (author) 17 refs., 5 figs

  13. Nonlinear propagation of a spatially incoherent laser beam: self-induced smoothing and reduction of scattering instabilities

    International Nuclear Information System (INIS)

    Maximov, A.V.; Ourdev, I.G.; Rozmus, W.; Capjack, C.E.; Mounaix, Ph.; Huller, S.; Pesme, D.; Tikhonchuk, V.T.; Divol, L.

    2000-01-01

    It is shown that plasma-induced angular spreading and spectral broadening of a spatially incoherent laser beam correspond to increased spatial and temporal incoherence of the laser light. The spatial incoherence is characterized by an effective beam f-number, decreasing in space along the direction of light propagation. Plasma-induced beam smoothing can influence laser-plasma interaction physics. In particular, decreasing the correlation time of the propagating laser light may dramatically reduce the levels of backward stimulated Brillouin and Raman scattering inside the plasma. Also, the decrease of the laser beam effective f-number reduces the reflectivity of backward stimulated Brillouin scattering. (authors)

  14. Theoretical studies on rapid fluctuations in solar flares

    International Nuclear Information System (INIS)

    Vlahos, L.

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins, e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed

  15. Theoretical studies on rapid fluctuations in solar flares

    Science.gov (United States)

    Vlahos, Loukas

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed.

  16. Orbital Noise in the Earth System and Climate Fluctuations

    Science.gov (United States)

    Liu, Han-Shou; Smith, David E. (Technical Monitor)

    2001-01-01

    Frequency noise in the variations of the Earth's obliquity (tilt) can modulate the insolation signal for climate change. Including this frequency noise effect on the incoming solar radiation, we have applied an energy balance climate model to calculate the climate fluctuations for the past one million years. Model simulation results are in good agreement with the geologically observed paleoclimate data. We conclude that orbital noise in the Earth system may be the major cause of the climate fluctuation cycles.

  17. Depth-resolved incoherent and coherent wide-field high-content imaging (Conference Presentation)

    Science.gov (United States)

    So, Peter T.

    2016-03-01

    Recent advances in depth-resolved wide-field imaging technique has enabled many high throughput applications in biology and medicine. Depth resolved imaging of incoherent signals can be readily accomplished with structured light illumination or nonlinear temporal focusing. The integration of these high throughput systems with novel spectroscopic resolving elements further enable high-content information extraction. We will introduce a novel near common-path interferometer and demonstrate its uses in toxicology and cancer biology applications. The extension of incoherent depth-resolved wide-field imaging to coherent modality is non-trivial. Here, we will cover recent advances in wide-field 3D resolved mapping of refractive index, absorbance, and vibronic components in biological specimens.

  18. Production of flat KrF laser focal profiles with echelon free-induced spatial incoherence

    International Nuclear Information System (INIS)

    Deniz, A.V.; Obenschain, S.P.; Pronko, M.; Lehmberg, R.H.

    1990-01-01

    High gain direct-drive laser fusion requires a uniform spherical pellet implosion. This in turn requires that the focal profile of each driving beam be sufficiently uniform and controlled. Several methods for producing uniform beams have been proposed. One promising technique, echelon free-induced spatial incoherence (ISI), consists of propagating a broadband spatially incoherent beam through an entire laser system. This technique will be used in the Nike laser, which is a twenty-four- to forty-eight-beam multikilojoule KrF system currently under construction at the Naval Research Laboratory (NRL). This paper presents measurements of focal profiles of laser light smoothed by echelon free ISI from a KrF oscillator and amplifier. The initial implementation is shown

  19. Compressive sensing sectional imaging for single-shot in-line self-interference incoherent holography

    Science.gov (United States)

    Weng, Jiawen; Clark, David C.; Kim, Myung K.

    2016-05-01

    A numerical reconstruction method based on compressive sensing (CS) for self-interference incoherent digital holography (SIDH) is proposed to achieve sectional imaging by single-shot in-line self-interference incoherent hologram. The sensing operator is built up based on the physical mechanism of SIDH according to CS theory, and a recovery algorithm is employed for image restoration. Numerical simulation and experimental studies employing LEDs as discrete point-sources and resolution targets as extended sources are performed to demonstrate the feasibility and validity of the method. The intensity distribution and the axial resolution along the propagation direction of SIDH by angular spectrum method (ASM) and by CS are discussed. The analysis result shows that compared to ASM the reconstruction by CS can improve the axial resolution of SIDH, and achieve sectional imaging. The proposed method may be useful to 3D analysis of dynamic systems.

  20. Transformation of EIA to EIT by incoherent pumping of the 85Rb D1 line

    Science.gov (United States)

    Yu, Hoon; Kim, Jung Dong; Jung, Tae Young; Kim, Jung Bog

    2012-10-01

    We have observed a transformation from electromagnetically-induced absorption (EIA) to electromagnetically induced transparency (EIT) in open systems of the 85Rb D1 line by adding an incoherent optical pumping laser. This result raises a new question about recent theoretical work which does not address the degree of open. The pump beam only plays a role in transferring atoms by a spontaneous transition into the interacting system for EIT observation, which is an incoherent process. The dependence of the absorption spectra on the intensity and the polarization of each laser beam were observed. We have found the same tendencies in all transitions except the F = 2 ↔ F' = 3 transition of the 85Rb D1 line, which is the system that almost satisfies conventional EIA conditions.

  1. Incoherent scattering of gamma photons for non-destructive tomographic inspection of pipeline

    International Nuclear Information System (INIS)

    Sharma, Amandeep; Sandhu, B.S.; Singh, Bhajan

    2010-01-01

    A scanner system, operating in a non-destructive and non-invasive way, is presented for pipeline to determine its location in land soil, wall thickness, type of liquid flowing and crack/blockage position. The present experiment simulates a real case where pipe corrosion (wall thinning) under insulation can be known from the study of incoherent scattering of 662 keV gamma photons. The incoherent scattered intensity, obtained by unfolding (deconvolution) the experimental pulse-height distribution of NaI(Tl) scintillation detector with the help of inverse response matrix, provides the desired information. The method is quite sensitive for small change (∼1 mm) in the thickness of pipe wall, locating a defect of 1 mm width under insulation and a small change (∼0.1 gm cm -3 ) in the density of liquid flowing through pipe.

  2. Vibronic dephasing model for coherent-to-incoherent crossover in DNA

    Science.gov (United States)

    Karasch, Patrick; Ryndyk, Dmitry A.; Frauenheim, Thomas

    2018-05-01

    In this paper, we investigate the interplay between coherent and incoherent charge transport in cytosine-guanine (GC-) rich DNA molecules. Our objective is to introduce a physically grounded approach to dephasing in large molecules and to understand the length-dependent charge transport characteristics, and especially the crossover from the coherent tunneling to incoherent hopping regime at different temperatures. Therefore, we apply the vibronic dephasing model and compare the results to the Büttiker probe model which is commonly used to describe decoherence effects in charge transport. Using the full ladder model and simplified one-dimensional model of DNA, we consider molecular junctions with alternating and stacked GC sequences and compare our results to recent experimental measurements.

  3. Formation of 2D bright spatial solitons in lithium niobate with photovoltaic response and incoherent background

    Science.gov (United States)

    Pustozerov, A.; Shandarov, V.

    2017-12-01

    The influence of incoherent background illumination produced by light-emitting diodes (LED's) of different average wavelengths and laser diode emitting in blue region of visible on diffraction characteristics of narrow coherent light beams of He-Ne laser due to refractive index changes of Fe-doped lithium niobate sample are studied. It has been experimentally demonstrated that nonlinear diffraction of red beams with wavelength 633 nm and diameters on full width of half maximum (FWHM) near to 15 μm may be totally compensated using background light with average wavelengths 450 - 465 nm. To provide the necessary intensity of incoherent background, the combinations of spherical and cylindrical concave lenses with blue LED and laser diode module without focusing its beam have been used.

  4. Bound coherent and incoherent thermal neutron scattering cross sections of the elements

    International Nuclear Information System (INIS)

    Sears, V.F.

    1982-12-01

    An up-to-date table of bound coherent and incoherent thermal neutron scattering cross sections of the elements is presented. Values from two different data sources are calculated and compared. These sources are: (1) the free-atom cross sections listed in the Σbarn bookΣ and (2) the Julich scattering length tables. We also call attention to, and clarify, the confusion that exists in the literature concerning the sign of the imaginary part of the complex scattering length

  5. Dose and dose rate effects on coherent-to-incoherent transition of precipitates upon irradiation

    Institute of Scientific and Technical Information of China (English)

    LI Zhengchao

    2006-01-01

    A typical precipitation hardened alloy, Cu-Co dilute alloy was selected to study the precipitation behavior and irradiation effect on precipitates. It is found that the principal effect of ion irradiation on the coherent precipitates is loss of coherency, and TEM cross-section observations show that the fraction of the incoherent precipitates is dependent on dose but not on dose rate during heavy ion irradiation.

  6. Incoherent Manipulation of the Photoactive Yellow Protein Photocycle with Dispersed Pump-Dump-Probe Spectroscopy

    OpenAIRE

    Larsen, Delmar S.; van Stokkum, Ivo H. M.; Vengris, Mikas; van der Horst, Michael A.; de Weerd, Frank L.; Hellingwerf, Klaas J.; van Grondelle, Rienk

    2004-01-01

    Photoactive yellow protein is the protein responsible for initiating the ``blue-light vision¿¿ of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast pump-dump-probe spectroscopy, where the photocycle can be started and interrupted with appropriately tuned and timed laser pulses. This ``incoherent¿¿ manipulation of the photocycle allows for the d...

  7. Fluctuation Relations for Currents

    Science.gov (United States)

    Sinitsyn, Nikolai; Akimov, Alexei; Chernyak, Vladimir; Chertkov, Michael

    2011-03-01

    We consider a non-equilibrium statistical system on a graph or a network. Identical particles are injected, interact with each other, traverse, and leave the graph in a stochastic manner described in terms of Poisson rates, possibly strongly dependent on time and instantaneous occupation numbers at the nodes of the graph. We show that the system demonstrates a profound statistical symmetry, leading to new Fluctuation Relations that originate from the supersymmetry and the principle of the geometric universality of currents rather than from the relations between probabilities of forward and reverse trajectories. NSF/ECCS-0925618, NSF/CHE-0808910 and DOE at LANL under Contract No. DE-AC52-06NA25396.

  8. Coherent and incoherent J /ψ photonuclear production in an energy-dependent hot-spot model

    Science.gov (United States)

    Cepila, J.; Contreras, J. G.; Krelina, M.

    2018-02-01

    In a previous publication, we have presented a model for the photoproduction of J /ψ vector mesons off protons, where the proton structure in the impact-parameter plane is described by an energy-dependent hot-spot profile. Here we extend this model to study the photonuclear production of J /ψ vector mesons in coherent and incoherent interactions of heavy nuclei. We study two methods to extend the model to the nuclear case: using the standard Glauber-Gribov formalism and using geometric scaling to obtain the nuclear saturation scale. We find that the incoherent cross section changes sizably with the inclusion of subnucleonic hot spots and that this change is energy dependent. We propose to search for this behavior by measuring the ratio of the incoherent to coherent cross sections at different energies. We compare the results of our model to results from the Relativistic Heavy-Ion Collider (RHIC) and from run 1 at the Large Hadron Collider (LHC), finding satisfactory agreement. We also present predictions for the LHC at the new energies reached in run 2. The predictions include J /ψ production in ultraperipheral collisions, as well as the recently observed photonuclear production in peripheral collisions.

  9. Coherent radiation from pulsars

    International Nuclear Information System (INIS)

    Cox, J.L. Jr.

    1979-01-01

    Interaction between a relativistic electrom stream and a plasma under conditions believed to exist in pulsar magnetospheres is shown to result in the simultaneous emission of coherent curvature radiation at radio wavelengths and incoherent curvature radiation at X-ray wavelengths from the same spatial volume. It is found that such a stream can propagate through a plasma parallel to a very strong magnetic field only if its length is less than a critical length L/sub asterisk/ic. Charge induced in the plasma by the stream co-moves with the stream and has the same limitation in longitudinal extent. The resultant charge bunching is sufficient to cause the relatively low energy plasma particles to radiate at radio wavelengths coherently while the relatively high energy stream particles radiate at X-ray wavelengths incoherently as the stream-plasma system moves along curved magnetic field lines. The effective number of coherently radiating particles per bunch is estimated to be approx.10 14 --10 15 for a tupical pulsar

  10. Fluctuations in email size

    Science.gov (United States)

    Matsubara, Yoshitsugu; Musashi, Yasuo

    2017-12-01

    The purpose of this study is to explain fluctuations in email size. We have previously investigated the long-term correlations between email send requests and data flow in the system log of the primary staff email server at a university campus, finding that email size frequency follows a power-law distribution with two inflection points, and that the power-law property weakens the correlation of the data flow. However, the mechanism underlying this fluctuation is not completely understood. We collected new log data from both staff and students over six academic years and analyzed the frequency distribution thereof, focusing on the type of content contained in the emails. Furthermore, we obtained permission to collect "Content-Type" log data from the email headers. We therefore collected the staff log data from May 1, 2015 to July 31, 2015, creating two subdistributions. In this paper, we propose a model to explain these subdistributions, which follow log-normal-like distributions. In the log-normal-like model, email senders -consciously or unconsciously- regulate the size of new email sentences according to a normal distribution. The fitting of the model is acceptable for these subdistributions, and the model demonstrates power-law properties for large email sizes. An analysis of the length of new email sentences would be required for further discussion of our model; however, to protect user privacy at the participating organization, we left this analysis for future work. This study provides new knowledge on the properties of email sizes, and our model is expected to contribute to the decision on whether to establish upper size limits in the design of email services.

  11. Fluctuating Thermodynamics for Biological Processes

    Science.gov (United States)

    Ham, Sihyun

    Because biomolecular processes are largely under thermodynamic control, dynamic extension of thermodynamics is necessary to uncover the mechanisms and driving factors of fluctuating processes. The fluctuating thermodynamics technology presented in this talk offers a practical means for the thermodynamic characterization of conformational dynamics in biomolecules. The use of fluctuating thermodynamics has the potential to provide a comprehensive picture of fluctuating phenomena in diverse biological processes. Through the application of fluctuating thermodynamics, we provide a thermodynamic perspective on the misfolding and aggregation of the various proteins associated with human diseases. In this talk, I will present the detailed concepts and applications of the fluctuating thermodynamics technology for elucidating biological processes. This work was supported by Samsung Science and Technology Foundation under Project Number SSTF-BA1401-13.

  12. Big Bang or vacuum fluctuation

    International Nuclear Information System (INIS)

    Zel'dovich, Ya.B.

    1980-01-01

    Some general properties of vacuum fluctuations in quantum field theory are described. The connection between the ''energy dominance'' of the energy density of vacuum fluctuations in curved space-time and the presence of singularity is discussed. It is pointed out that a de-Sitter space-time (with the energy density of the vacuum fluctuations in the Einstein equations) that matches the expanding Friedman solution may describe the history of the Universe before the Big Bang. (P.L.)

  13. Thermodynamic theory of equilibrium fluctuations

    International Nuclear Information System (INIS)

    Mishin, Y.

    2015-01-01

    The postulational basis of classical thermodynamics has been expanded to incorporate equilibrium fluctuations. The main additional elements of the proposed thermodynamic theory are the concept of quasi-equilibrium states, a definition of non-equilibrium entropy, a fundamental equation of state in the entropy representation, and a fluctuation postulate describing the probability distribution of macroscopic parameters of an isolated system. Although these elements introduce a statistical component that does not exist in classical thermodynamics, the logical structure of the theory is different from that of statistical mechanics and represents an expanded version of thermodynamics. Based on this theory, we present a regular procedure for calculations of equilibrium fluctuations of extensive parameters, intensive parameters and densities in systems with any number of fluctuating parameters. The proposed fluctuation formalism is demonstrated by four applications: (1) derivation of the complete set of fluctuation relations for a simple fluid in three different ensembles; (2) fluctuations in finite-reservoir systems interpolating between the canonical and micro-canonical ensembles; (3) derivation of fluctuation relations for excess properties of grain boundaries in binary solid solutions, and (4) derivation of the grain boundary width distribution for pre-melted grain boundaries in alloys. The last two applications offer an efficient fluctuation-based approach to calculations of interface excess properties and extraction of the disjoining potential in pre-melted grain boundaries. Possible future extensions of the theory are outlined.

  14. Enhanced coherent undulator radiation from bunched electron beams

    International Nuclear Information System (INIS)

    Berryman, K.W.; Crosson, E.R.; Ricci, K.N.; Smith, T.I.

    1996-01-01

    When energetic bunches of electrons traverse an undulator field, they can spontaneously emit radiation both coherently and incoherently. Although it has generally been assumed that undulator radiation is incoherent at wavelengths short compared to the longitudinal size of the electron bunch, several recent observations have proved this assumption false. Furthermore, the appearance of coherent radiation is often accompanied by a significant increase in radiated power. Here we report observations of strongly enhanced coherent spontaneous radiation together with direct measurements, using transition radiation techniques, of the electron distributions responsible for the coherent emission. We also report demonstrated enhancements in the predicted spontaneous radiated power by as much as 6x10 4 using electron bunch compression. copyright 1996 American Institute of Physics

  15. Magnetic fluctuations associated with density fluctuations in the tokamak edge

    International Nuclear Information System (INIS)

    Kim, Y.J.; Gentle, K.W.; Ritz, C.P.; Rhodes, T.L.; Bengtson, R.D.

    1989-01-01

    Electrostatic density and potential fluctuations occurring with high amplitude near the edge of a tokamak are correlated with components of the fluctuating magnetic field measured outside the limiter radius. It has been established that this turbulence is associated with fluctuations in current as well as density and potential. The correlation extends for substantial toroidal distances, but only if the probes are displaced approximately along field lines, consistent with the short coherence lengths poloidally but long coherence lengths parallel to the field which are characteristic for this turbulence. Furthermore, the correlation can be found only with density fluctuations measured inside the limiter radius; density fluctuations behind the limiter have no detectable magnetic concomitant for the toroidally spaced probes used here. (author). Letter-to-the-editor. 12 refs, 3 figs

  16. Charge Fluctuations in Nanoscale Capacitors

    NARCIS (Netherlands)

    Limmer, D.T.; Merlet, C.; Salanne, M.; Chandler, D.; Madden, P.A.; van Roij, R.H.H.G.; Rotenberg, B.

    2013-01-01

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with

  17. Fluctuating attention in Parkinson's disease

    DEFF Research Database (Denmark)

    Starrfelt, Randi; Aarsland, Dag; Janvin, Carmen

    2001-01-01

    Lewy body dementia (DLB), which share many clinical and pathological features with Parkinson’s disease (PD), is charac- terised by marked fluctuations in cognition and consciousness. Fluctuating cognition has not been formally studied in PD, although some studies indicate that PD patients show...

  18. Early evaluation of irradiated parotid glands with intravoxel incoherent motion MR imaging: correlation with dynamic contrast-enhanced MR imaging

    International Nuclear Information System (INIS)

    Zhou, Nan; Chu, Chen; Dou, Xin; Li, Ming; Liu, Song; Zhu, Lijing; Liu, Baorui; Guo, Tingting; Chen, Weibo; He, Jian; Yan, Jing; Zhou, Zhengyang; Yang, Xiaofeng; Liu, Tian

    2016-01-01

    Radiation-induced parotid damage is one of the most common complications in patients with nasopharyngeal carcinoma (NPC) undergoing radiotherapy (RT). Intravoxel incoherent motion (IVIM) magnetic resonance (MR) imaging has been reported for evaluating irradiated parotid damage. However, the changes of IVIM perfusion-related parameters in irradiated parotid glands have not been confirmed by conventional perfusion measurements obtained from dynamic contrast-enhanced (DCE) MR imaging. The purposes of this study were to monitor radiation-induced parotid damage using IVIM and DCE MR imaging and to investigate the correlations between changes of these MR parameters. Eighteen NPC patients underwent bilateral parotid T1-weighted, IVIM and DCE MR imaging pre-RT (2 weeks before RT) and post-RT (4 weeks after RT). Parotid volume; IVIM MR parameters, including apparent diffusion coefficient (ADC), pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f); and DCE MR parameters, including maximum relative enhancement (MRE), time to peak (TTP), Wash in Rate, and the degree of xerostomia were recorded. Correlations of parotid MR parameters with mean radiation dose, atrophy rate and xerostomia degree, as well as the relationships between IVIM and DCE MR parameters, were investigated. From pre-RT to post-RT, all of the IVIM and DCE MR parameters increased significantly (p < 0.001 for ADC, D, f, MRE, Wash in Rate; p = 0.024 for D*; p = 0.037 for TTP). Change rates of ADC, f and MRE were negatively correlated with atrophy rate significantly (all p < 0.05). Significant correlations were observed between the change rates of D* and MRE (r = 0.371, p = 0.026) and between the change rates of D* and TTP (r = 0.396, p = 0.017). The intra- and interobserver reproducibility of IVIM and DCE MR parameters was good to excellent (intraclass correlation coefficient, 0.633–0.983). Early radiation-induced changes of parotid glands could be evaluated by IVIM and

  19. A new analysis of radiation-induced cytogenetic damage in human lymphocytes using the PCC technique, and its implications for biological dosimetry and the understanding of cell-cycle-dependent radiosensitivity fluctuations

    International Nuclear Information System (INIS)

    Zannos, A.; Pantelias, G.E.

    1993-01-01

    The objectives of the project are: to develop a sensitive biological dosemeter, based on the analysis of C-banded peripheral blood lymphocyte prematurely condensed chromosomes (PCCs), for the early assessment of radiation injury and the establishment of absorbed dose estimates in accidental overexposures; and to elucidate the mechanisms of radiation action at the molecular, chromosomal and cellular levels by the study of the effects of DNA repair inhibitors on the repair of radiation damage, effects of BrdUrd incorporation on radiation damage, effects of hyperthermia on the induction and repair of radiation-induced damage, and induction and repair of radiation damage in an X-ray sensitive CHO mutant cell line. (authors) 16 refs., 1 fig

  20. Nonequilibrium fluctuations in a resistor.

    Science.gov (United States)

    Garnier, N; Ciliberto, S

    2005-06-01

    In small systems where relevant energies are comparable to thermal agitation, fluctuations are of the order of average values. In systems in thermodynamical equilibrium, the variance of these fluctuations can be related to the dissipation constant in the system, exploiting the fluctuation-dissipation theorem. In nonequilibrium steady systems, fluctuations theorems (FT) additionally describe symmetry properties of the probability density functions (PDFs) of the fluctuations of injected and dissipated energies. We experimentally probe a model system: an electrical dipole driven out of equilibrium by a small constant current I, and show that FT are experimentally accessible and valid. Furthermore, we stress that FT can be used to measure the dissipated power P = R I2 in the system by just studying the PDFs' symmetries.

  1. Quantum fluctuations from thermal fluctuations in Jacobson formalism

    Energy Technology Data Exchange (ETDEWEB)

    Faizal, Mir [University of British Columbia-Okanagan, Irving K. Barber School of Arts and Sciences, Kelowna, BC (Canada); University of Lethbridge, Department of Physics and Astronomy, Lethbridge, AB (Canada); Ashour, Amani; Alcheikh, Mohammad [Damascus University, Mathematics Department, Faculty of Science, Damascus (Syrian Arab Republic); Alasfar, Lina [Universite Clermont Auvergne, Laboratoire de Physique Corpusculaire de Clermont-Ferrand, Aubiere (France); Alsaleh, Salwa; Mahroussah, Ahmed [King Saud University, Department of Physics and Astronomy, Riyadh (Saudi Arabia)

    2017-09-15

    In the Jacobson formalism general relativity is obtained from thermodynamics. This is done by using the Bekenstein-Hawking entropy-area relation. However, as a black hole gets smaller, its temperature will increase. This will cause the thermal fluctuations to also increase, and these will in turn correct the Bekenstein-Hawking entropy-area relation. Furthermore, with the reduction in the size of the black hole, quantum effects will also start to dominate. Just as the general relativity can be obtained from thermodynamics in the Jacobson formalism, we propose that the quantum fluctuations to the geometry can be obtained from thermal fluctuations. (orig.)

  2. Analysis of differential method for compensating fluctuations in product thickness when radiometric testing

    International Nuclear Information System (INIS)

    Pokrovskij, A.V.; Kvasnitsa, M.S.

    1979-01-01

    Given are the estimates of information capabilities of the differential method for measuring radiation flux in radiation defectoscopy as well as efficiency of application of automatic radiation facilities to control taking into account the statistical regularities of product thickness fluctuations. Dependences of signal to noise ratio on the regularities of product thickness fluctuations have been found and optimization, on this basis, of the design and parameters of processing instrumentation was carried out. It is shown, that with 60-80 mm interval of product thickness fluctuations correlation (welded joints) it is expedient to use two radiation beams with their crossing on a mean product plane. When the interval of correlation of thickness fluctuations is great it is effective to use the geometry of radioscopy with parallel radiation beams. This permits to use only one radiation source without significant reducing the compensation efficiency, that in most cases simplifies the development and application of radiometric systems. Thus the efficiency of applying the differential method for radiation beam detection to compensate product thickness fluctuations is primarily determined by statistical regularities of the given fluctuations. The account of the regularities in the development of the processing instrumentation results in the most complete extraction of useful information, containing in the radiation beams being detected

  3. Lower thermospheric neutral densities determined from Soendre Stroemfjord incoherent scatter radar during LTCS 1

    International Nuclear Information System (INIS)

    Reese, K.W.; Johnson, R.M.; Killeen, T.L.

    1991-01-01

    Ion-neutral collision frequencies determined from measurements obtained by the incoherent scatter radar located at Soendre Stroemfjord, Greenland, have been used to derive lower thermospheric neutral densities during the first Lower Thermosphere Coupling Study (LTCS 1), September 21-26, 1987. Periods of Joule and particle heating which might disturb the E region thermal equilibrium were systematically eliminated. The mean profile of neutral density for the period is in good agreement with the mass spectrometer incoherent scatter 1986 (MSIS-86) model between 92 and 104 km. A tendency to overestimate collision frequencies above 105 km may arise from range-smearing effects. The results of a tidal analysis performed on the neutral density between 92 and 109 km show that the amplitudes of the diurnal and semidiurnal components of the tides are approximately equivalent. The observations are generally in better agreement with the MSIS-86 predictions than with the thermosphere-ionosphere general circulation model (TIGCM) simulation of the LTCS 1 interval. The observed phase of the diurnal component is approximately constant with height above 98 km and is in close agreement with the MSIS-86 model phases; however, the TIGCM diurnal phases are shifted by 6-8 hours to later local times. The phase of the semidiurnal tide is in good agreement with predictions of the MSIS-86 model and the TIGCM simulation of this interval, except near 98 km. The observed semidiurnal phase is also consistent with previous high-latitude results (Kirkwood, 1986). The relative amplitude of the observed semidiurnal oscillation is up to 15% larger than that previously observed at the European Incoherent Scatter facility but is consistent with the amplitudes presented in an earlier study of Millstone Hill measurements (Salah, 1974)

  4. A simulation experiment and analysis on the effects of in-coherence in fuel coolant interaction

    International Nuclear Information System (INIS)

    Kondo, S.; Togo, Y.; Iwamura, T.

    1976-01-01

    Experimental and analytical studies were conducted to investigate effects of incoherence (space time behavior of molten fuel) on molten fuel coolant interaction. In experiments, a 2 mm diameter molten tin jet was injected upward into the water in a slender tank. The results were analyzed based on the pressure records and high speed photographs. The pressure records indicated that there were two types of interaction between molten jet and water, intermittent explosion mode and continuous one. The explosion mode appeared when the temperature of molten tin was above 350 0 C or so and that of water was below 70 0 C or so. The high speed photograph indicated that an establishment of a stable jet column was necessary for an explosive interaction and that a bubble like region grew and collapsed at the root of the jet in accordance with the generation of pressure pulse. It was found that the mass of metal which contributed to the vapor explosion was only a small part of the injected metal in the case of jet injection type contact mode and this was the reason why the gross thermal to mechanical energy conversion ratio was around 0.03% in this type of contact mode, though this ratio was around 2% if only the part of record around the pressure pulse was taken into consideration. In the analysis part, a multi-channel FCI model was developed to evaluate the spatial incoherence effect on pressure at subassembly exit. The calculated pressure trace indicated that the spatial incoherence has considerable effects for an evaluation of structure response under FCI pressure loading. (auth.)

  5. Spatially continuous approach to the description of incoherencies in fast reactor accident analysis

    International Nuclear Information System (INIS)

    Luck, L.B.

    1976-12-01

    A generalized cell-type approach is developed in which individual subassemblies are represented as a unit. By appropriate characterization of the results of separate detailed investigations, spatial variations within a cell are represented as a superposition. The advantage of this approach is that costly detailed cell-type information is generated only once or a very few times. Spatial information obtained by the cell treatment is properly condensed in order to drastically reduce the transient computation time. Approximate treatments of transient phenomena are developed based on the use of distributions of volume and reactivity worth with temperature and other reactor parameters. Incoherencies during transient are physically dependent on the detailed variations in the initial state. Therefore, stationary volumetric distributions which contain in condensed form the detailed initial incoherency information provides a proper basis for the transient treatment. Approximate transient volumetric distributions are generated by a suitable transformation of the stationary distribution to reflect the changes in the transient temperature field. Evaluation of transient changes is based on results of conventional uniform channel calculations and a superposition of lateral variations as they are derived from prior cell investigations. Specific formulations are developed for the treatment of reactivity feedback. Doppler and sodium expansion reactivity feedback is related to condensed temperature-worth distributions. Transient evaluation of the worth distribution is based on the relation between stationary and transient volumetric distributions, which contains the condensed temperature field information. Coolant voiding is similarly treated with proper distribution information. Results show that the treatments developed for the transient phase up to and including sodium boiling constitute a fast and effective simulation of inter- and intra-subassembly incoherence effects

  6. Parametric instabilities of parallel propagating incoherent Alfven waves in a finite ion beta plasma

    International Nuclear Information System (INIS)

    Nariyuki, Y.; Hada, T.; Tsubouchi, K.

    2007-01-01

    Large amplitude, low-frequency Alfven waves constitute one of the most essential elements of magnetohydrodynamic (MHD) turbulence in the fast solar wind. Due to small collisionless dissipation rates, the waves can propagate long distances and efficiently convey such macroscopic quantities as momentum, energy, and helicity. Since loading of such quantities is completed when the waves damp away, it is important to examine how the waves can dissipate in the solar wind. Among various possible dissipation processes of the Alfven waves, parametric instabilities have been believed to be important. In this paper, we numerically discuss the parametric instabilities of coherent/incoherent Alfven waves in a finite ion beta plasma using a one-dimensional hybrid (superparticle ions plus an electron massless fluid) simulation, in order to explain local production of sunward propagating Alfven waves, as suggested by Helios/Ulysses observation results. Parameter studies clarify the dependence of parametric instabilities of coherent/incoherent Alfven waves on the ion and electron beta ratio. Parametric instabilities of coherent Alfven waves in a finite ion beta plasma are vastly different from those in the cold ions (i.e., MHD and/or Hall-MHD systems), even if the collisionless damping of the Alfven waves are neglected. Further, ''nonlinearly driven'' modulational instability is important for the dissipation of incoherent Alfven waves in a finite ion beta plasma regardless of their polarization, since the ion kinetic effects let both the right-hand and left-hand polarized waves become unstable to the modulational instability. The present results suggest that, although the antisunward propagating dispersive Alfven waves are efficiently dissipated through the parametric instabilities in a finite ion beta plasma, these instabilities hardly produce the sunward propagating waves

  7. Single-shot fluctuations in waveguided high-harmonic generation

    NARCIS (Netherlands)

    Goh, S.J.; Tao, Y.; van der Slot, Petrus J.M.; Bastiaens, Hubertus M.J.; Herek, Jennifer Lynn; Biedron, S.G.; Danailov, M.B.; Milton, S.V.; Boller, Klaus J.

    2015-01-01

    For exploring the application potential of coherent soft x-ray (SXR) and extreme ultraviolet radiation (XUV) provided by high-harmonic generation, it is important to characterize the central output parameters. Of specific importance are pulse-to-pulse (shot-to-shot) fluctuations of the high-harmonic

  8. Experimental evidence of significant temperature fluctuations in the plasma EDGE region of the TJ-I Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Hidalgo, C; Balbin, R; Pedrosa, M A; Garcia-Cortes, I; Ochando, M A

    1993-07-01

    Density and temperature fluctuations have been measured in the plasma bulk side of the velocity shear location of the TJ-I tokamak using a feast swept Langmuir probe technique. Evidence of substantial temperature fluctuations which are in phase close to opposition with the corresponding density fluctuations has been found. This result suggests the possible role of radiation in determining edge fluctuation levels and call into question the determination of the density and potential fluctuations from the Langmuir current-probe and floating potential fluctuations. (Author) 16 refs.

  9. Experimental evidence of significant temperature fluctuations in the plasma edge region of the TJ-I Tokamak

    International Nuclear Information System (INIS)

    Hidalgo, C.; Balbin, R.; Pedrosa, M.A.; Garcia-Cortes, I.; Ochando, M.A.

    1993-01-01

    Density and temperature fluctuations have been measured in the plasma bulk side of the velocity shear location of the TJ-I tokamak using a foast swept Langmuir probe technique. Evidence of sustantial temperature fluctuations which are in phase close to opposition with the corresponding density fluctuations has been found. This result suggests the possible role of radiation in determining edge fluctuation levels and call into question the determination of the density and potential fluctuations from the Langmuir current-probe and floating potential fluctuations. (Author)

  10. Experimental evidence of significant temperature fluctuations in the plasma EDGE region of the TJ-I Tokamak

    International Nuclear Information System (INIS)

    Hidalgo, C.; Balbin, R.; Pedrosa, M. A.; Garcia-Cortes, I.; Ochando, M. A.

    1993-01-01

    Density and temperature fluctuations have been measured in the plasma bulk side of the velocity shear location of the TJ-I tokamak using a feast swept Langmuir probe technique. Evidence of substantial temperature fluctuations which are in phase close to opposition with the corresponding density fluctuations has been found. This result suggests the possible role of radiation in determining edge fluctuation levels and call into question the determination of the density and potential fluctuations from the Langmuir current-probe and floating potential fluctuations. (Author) 16 refs

  11. Current density fluctuations and ambipolarity of transport

    International Nuclear Information System (INIS)

    Shen, W.; Dexter, R.N.; Prager, S.C.

    1991-10-01

    The fluctuation in the plasma current density is measured in the MIST reversed field pinch experiment. Such fluctuations, and the measured radial profile of the k spectrum of magnetic fluctuations, supports the view and that low frequency fluctuations (f r >) demonstrates that radial particle transport from particle motion parallel to a fluctuating magnetic field is ambipolar over the full frequency range

  12. Misplaced Idealism and Incoherent Realism in the Philosophy of the Refugee Crisis

    DEFF Research Database (Denmark)

    Lægaard, Sune

    2016-01-01

    Many contributions to the philosophical debate about conceptual and normative issues raised by the refugee crisis fail to take properly account of the difference between ideal and nonideal theory. This makes several otherwise interesting and apparently plausible contributions to the philosophy...... of arguments about how we should understand or respond to the refugee crisis, which appear to offer coherent principles for the moral guidance of political actors but which are actually incoherent as principles of practical reasoning for the context they aim to address....

  13. Incoherent neutron scattering functions for random jump diffusion in bounded and infinite media

    International Nuclear Information System (INIS)

    Hall, P.L.; Ross, D.K.

    1981-01-01

    The incoherent neutron scattering function for unbounded jump diffusion is calculated from random walk theory assuming a gaussian distribution of jump lengths. The method is then applied to calculate the scattering function for spatially bounded random jumps in one dimension. The dependence on momentum transfer of the quasi-elastic energy broadenings predicted by this model and a previous model for bounded one-dimensional continuous diffusion are calculated and compared with the predictions of models for diffusion in unbounded media. The one-dimensional solutions can readily be generalized to three dimensions to provide a description of quasi-elastic scattering of neutrons by molecules undergoing localized random motions. (author)

  14. From Coherently Excited Highly Correlated States to Incoherent Relaxation Processes in Semiconductors

    International Nuclear Information System (INIS)

    Scha''fer, W.; Lo''venich, R.; Fromer, N. A.; Chemla, D. S.

    2001-01-01

    Recent theories of highly excited semiconductors are based on two formalisms, referring to complementary experimental conditions, the real-time nonequilibrium Green's function techniques and the coherently controlled truncation of the many-particle problem. We present a novel many-particle theory containing both of these methods as limiting cases. As a first example of its application, we investigate four-particle correlations in a strong magnetic field including dephasing resulting from the growth of incoherent one-particle distribution functions. Our results are the first rigorous solution concerning formation and decay of four-particle correlations in semiconductors. They are in excellent agreement with experimental data

  15. Anomalous vibrational modes in acetanilide: A F.D.S. incoherent inelastic neutron scattering study

    International Nuclear Information System (INIS)

    Barthes, M.; Moret, J.; Eckert, J.; Johnson, S.W.; Swanson, B.I.; Unkefer, C.J.

    1991-01-01

    The origin of the anomalous infra-red and Raman modes in acetanilide (C 6 H 5 NHCOCH 3 , or ACN), remains a subject of considerable controversy. One family of theoretical models involves Davydov-like solitons nonlinear vibrational coupling, or ''polaronic'' localized modes. An alternative interpretation of the extra-bands in terms of a Fermi resonance was proposed and recently the existence of slightly non-degenerate hydrogen atom configurations in the H-bond was suggested as an explanation for the anomalies. In this paper we report some new results on the anomalous vibrational modes in ACN that were obtained by inelastic incoherent neutron scattering (INS)

  16. Coexistence of synchrony and incoherence in oscillatory media under nonlinear global coupling

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Lennart; García-Morales, Vladimir [Physik-Department, Nonequilibrium Chemical Physics, Technische Universität München, James-Franck-Str. 1, D-85748 Garching (Germany); Institute for Advanced Study, Technische Universität München, Lichtenbergstr. 2a, D-85748 Garching (Germany); Schönleber, Konrad; Krischer, Katharina, E-mail: krischer@tum.de [Physik-Department, Nonequilibrium Chemical Physics, Technische Universität München, James-Franck-Str. 1, D-85748 Garching (Germany)

    2014-03-15

    We report a novel mechanism for the formation of chimera states, a peculiar spatiotemporal pattern with coexisting synchronized and incoherent domains found in ensembles of identical oscillators. Considering Stuart-Landau oscillators, we demonstrate that a nonlinear global coupling can induce this symmetry breaking. We find chimera states also in a spatially extended system, a modified complex Ginzburg-Landau equation. This theoretical prediction is validated with an oscillatory electrochemical system, the electro-oxidation of silicon, where the spontaneous formation of chimeras is observed without any external feedback control.

  17. Microscopic theory of coherent and incoherent optical properties of semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Martin

    2008-09-02

    An important question is whether there is a regime in which lasing from indirect semiconductors is possible. Thus, we discuss this question in this thesis. It is shown that under incoherent emission conditions it is possible to create an exciton condensate in multiple-quantum-well (MQW) systems. The influence of a MQW structure on the exciton lifetime is investigated. For the description of the light-matter interaction of a QW in the coherent excitation regime, the semiconductor Bloch equation (SBE) are used. The incoherent regime is described by the semiconductor luminescence equations (SLE). In principle it is even possible to couple SBE and SLE. The resulting theory is able to describe interactions between coherent and incoherent processes we investigate both, the coherent and the incoherent light-emission regime. Thus we define the investigated system and introduce the many-body Hamiltonian that describes consistently the light-matter interaction in the classical and the quantum limit. We introduce the SBE that allow to compute the light-matter interaction in the coherent scenario. The extended scattering model is used to investigate the absorption of a Ge QW for different time delays after the excitations. In this context, we analyze whether there is a regime in which optical gain can be realized. Then we apply a transfer-matrix method to include into our calculations the influence of the dielectric environment on the optical response. Thereafter the SLE for a MQW system are introduced. We derive a scheme that allows for decoupling environmental effects from the pure PL-emission properties of the QW. The PL of the actual QW system is obtained by multiplying this filter function and the free-space PL that describes the quantum emission into a medium with spatially constant background-refractive index. It is studied how the MQW-Bragg structure influences the PL-emission properties compared to the emission of a single QW device. As a last feature, it is shown

  18. All-fiber 7x1 signal combiner for incoherent laser beam combining

    DEFF Research Database (Denmark)

    Noordegraaf, Danny; Maack, Martin D.; Skovgaard, Peter M. W.

    2011-01-01

    We demonstrate an all-fiber 7x1 signal combiner for incoherent laser beam combining. This is a potential key component for reaching several kW of stabile laser output power. The combiner couples the output from 7 single-mode (SM) fiber lasers into a single multi-mode (MM) fiber. The input signal ...... in device temperature is observed. At an intermediate power level of 600 W a beam parameter product (BPP) of 2.22 mm x mrad is measured, corresponding to an M2 value of 6.5. These values are approaching the theoretical limit dictated by brightness conservation....

  19. Physical model for the incoherent writing/erasure of cavity solitons in semiconductor optical amplifiers.

    Science.gov (United States)

    Barbay, S; Kuszelewicz, R

    2007-09-17

    We present a physical mechanism that explains the recent observations of incoherent writing and erasure of Cavity Solitons in a semiconductor optical amplifier [S. Barbay et al, Opt. Lett. 31, 1504-1506 (2006)]. This mechanism allows to understand the main observations of the experiment. In particular it perfectly explains why writing and erasure are possible as a result of a local perturbation in the carrier density, and why a delay is observed along with the writing process. Numerical simulations in 1D are performed and show very good qualitative agreement with the experimental observations.

  20. Separation of coherent and incoherent scattering in liquid para-H{sub 2} by polarisation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Hernandez, M; Mompean, F J [Madrid Univ. (Spain); Schaerpf, O; Andersen, K H [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); Fak, B [CEA Centre d` Etudes de Grenoble, 38 (France)

    1997-04-01

    In the 1960 IAEA Symposium on Neutron Scattering, Sarma presented his theoretical study on the scattering of cold neutrons by liquid hydrogen and demonstrated how the intimate coupling between nuclear and rotational degrees of freedom finally results in the possibility of observing collective modes from this material, which to many neutron scatterers is synonymous with `incoherent`. This problem is investigated with polarised neutrons to gain access to a limited region of the (Q,E) space where the collective response from this liquid is found. (author).

  1. Analysis of the Spectral Efficiency of Frequency-Encoded OCDMA Systems With Incoherent Sources

    Science.gov (United States)

    Rochette, Martin; Ayotte, Simon; Rusch, Leslie A.

    2005-04-01

    This paper presents the spectral efficiency of frequency-encoded (FE) optical code-division multiple-access (OCDMA) systems with incoherent sources. The spectral efficiency of five code families compatible with FE-OCDMA is calculated as a function of the number of users. Analytical equations valid in the limiting case of Gaussian noise are also developed for the bit-error rate and the spectral efficiency. Among the code families considered, the modified quadratic congruence code leads to the maximum achievable spectral efficiency.

  2. Dynamics and Structural Details of Amorphous Phases of Ice Determined by Incoherent Inelastic Neutron Scattering

    International Nuclear Information System (INIS)

    Klug, D.D.; Tulk, C.A.; Svensson, E.C.; Loong, C.

    1999-01-01

    Incoherent-inelastic neutron scattering data are obtained over the energy range of lattice and internal vibrations of water molecules in phases of ice prepared by pressure-induced amorphization (high-density amorphous ice, hda), by thermal annealing of hda (low-density amorphous ice, lda), and by rapidly cooling water, as well as in ice Ih and Ic . Hydrogen bonding interactions in lda differ significantly from those in the glass obtained by rapid quenching, which has hydrogen-bond interactions characteristic of highly supercooled water. Hydrogen-bond interactions in hda are weaker than in the low-density phases. copyright 1999 The American Physical Society

  3. High-order UWB pulses scheme to generate multilevel modulation formats based on incoherent optical sources.

    Science.gov (United States)

    Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2013-11-18

    We present a high-order UWB pulses generator based on a microwave photonic filter which provides a set of positive and negative samples by using the slicing of an incoherent optical source and the phase inversion in a Mach-Zehnder modulator. The simple scalability and high reconfigurability of the system permit a better accomplishment of the FCC requirements. Moreover, the proposed scheme permits an easy adaptation to pulse amplitude modulation, bi phase modulation, pulse shape modulation and pulse position modulation. The flexibility of the scheme for being adaptable to multilevel modulation formats permits to increase the transmission bit rate by using hybrid modulation formats.

  4. Coherent versus incoherent dynamics in InAs quantum-dot active wave guides

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, W.; Hvam, Jørn Märcher

    2001-01-01

    Coherent dynamics measured by time-resolved four-wave mixing is compared to incoherent population dynamics measured by differential transmission spectroscopy on the ground-state transition at room temperature of two types of InAs-based quantum dots with different confinement energies. The measure....... The measurements are performed with heterodyne detection on quantum-dot active wave guides to enhance the light-matter interaction length. An elastic nature of the measured dephasing is revealed which is independent of the dot energy level scheme....

  5. Charged-particle incoherent-motion damping in storage rings by means of dissipative elements

    International Nuclear Information System (INIS)

    Derbenev, Ya.S.; Khejfets, S.A.

    1979-01-01

    In consecutive order a possibility of damping of beam incoherent oscillations in a storage ring was studied by means of an external dissipative system in a sufficient common case. It is shown, that a useful effect, as for the case of electron cooling, is one-particle effect of particle oscillations damping due to nonconservatism of its interaction with an external system. Each other mutual influence through the external system becomes significant with increasing beam density and results in the limitation to achievable damping decrements

  6. Observation of Coherent and Incoherent Dissociation Mechanisms in the Angular Distribution of Atomic Photofragment Alignment

    International Nuclear Information System (INIS)

    Bracker, A.S.; Lee, Y.T.; Bracker, A.S.; Wouters, E.R.; Suits, A.G.; Lee, Y.T.; Lee, Y.T.; Vasyutinskii, O.S.

    1998-01-01

    We have analyzed the recoil angle dependence of chlorine atom angular momentum alignment for the dissociation of chlorine molecules at 355nm. This angular distribution was isolated from ion image measurements, which map a three-dimensional velocity vector distribution of state-selectively-ionized photofragments into a two-dimensional spatial distribution. Using a general quantum mechanical method to simulate the alignment angular distribution, we show that there are clear contributions to alignment from both incoherent and coherent components of a perpendicular optical transition in the molecule. copyright 1998 The American Physical Society

  7. Three-Dimensional Imaging by Self-Reference Single-Channel Digital Incoherent Holography

    Science.gov (United States)

    Rosen, Joseph; Kelner, Roy

    2016-01-01

    Digital holography offers a reliable and fast method to image a three-dimensional scene from a single perspective. This article reviews recent developments of self-reference single-channel incoherent hologram recorders. Hologram recorders in which both interfering beams, commonly referred to as the signal and the reference beams, originate from the same observed objects are considered as self-reference systems. Moreover, the hologram recorders reviewed herein are configured in a setup of a single channel interferometer. This unique configuration is achieved through the use of one or more spatial light modulators. PMID:28757811

  8. Three-dimensional mapping of fluorescent nanoparticles using incoherent digital holography.

    Science.gov (United States)

    Yanagawa, Takumi; Abe, Ryosuke; Hayasaki, Yoshio

    2015-07-15

    Three-dimensional mapping of fluorescent nanoparticles was performed by using incoherent digital holography. The positions of the nanoparticles were quantitatively determined by using Gaussian fitting of the axial- and lateral-diffraction distributions through position calibration from the observation space to the sample space. It was found that the axial magnification was constant whereas the lateral magnification linearly depended on the axial position of the fluorescent nanoparticles. The mapping of multiple fluorescent nanoparticles fixed in gelatin and a single fluorescent nanoparticle manipulated with optical tweezers in water were demonstrated.

  9. Experimental study of coherent radiation in the millimeter-wave region at the KURRI-LINAC

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Toshiharu [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.

    1996-07-01

    Coherent radiation, i.e., synchrotron radiation, transition radiation, Cherenkov radiation, or Smith-Purcell radiation emitted by short bunches of electrons has been observed in the millimeter-wave region. Properties of coherent radiation are characterized by the coherence effect and the relativistic one. The intensity of coherent radiation is enormously enhanced by several orders of magnitude in comparison with the incoherent radiation and the flux of radiation concentrates around the direction of the electron beam. Coherent radiation is useful as the intense light source in the millimeter-wave region. (author)

  10. Localized description of valence fluctuations

    International Nuclear Information System (INIS)

    Alascio, B.; Allub, R.; Aligia, A.

    1979-07-01

    The authors set up a model for intermediate valence equivalent to the ''atomic'' limit of the Anderson Hamiltonian. Detailed analysis of this model shows that most of the essential characteristics of valence fluctuators are already present in this crudely simplified Hamiltonian. The spin-spin and the 4f charge-charge correlation functions are studied and it is shown that it is possible to define a spin fluctuation frequency ωsub(s.f.) and a charge fluctuation frequency ωsub(ch.f.).ωsub(s.f.) and ωsub(ch.f.) can differ considerably for some values of the parameters of the model. The magnetic susceptibility and the specific heat are calculated as functions of temperature and it is shown how the results simulate the behaviour found in valence fluctuators. (author)

  11. The Fluctuation Niche in Plants

    Directory of Open Access Journals (Sweden)

    Jaume Terradas

    2009-01-01

    Full Text Available Classical approaches to niche in coexisting plants have undervalued temporal fluctuations. We propose that fluctuation niche is an important dimension of the total niche and interacts with habitat and life-history niches to provide a better understanding of the multidimensional niche space where ecological interactions occur. To scale a fluctuation niche, it is necessary to relate environmental constrictions or species performance not only to the absolute values of the usual environmental and ecophysiological variables but also to their variances or other measures of variability. We use Mediterranean plant communities as examples, because they present characteristic large seasonal and interannual fluctuations in water and nutrient availabilities, along an episodic-constant gradient, and because the plant responses include a number of syndromes coupled to this gradient.

  12. The Fluctuation Niche in Plants

    International Nuclear Information System (INIS)

    Terradas, J.; Penuelas, J.; Lloret, F.; Penuelas, J.

    2009-01-01

    Classical approaches to niche in coexisting plants have undervalued temporal fluctuations. We propose that fluctuation niche is an important dimension of the total niche and interacts with habitat and life-history niches to provide a better understanding of the multidimensional niche space where ecological interactions occur. To scale a fluctuation niche, it is necessary to relate environmental constrictions or species performance not only to the absolute values of the usual environmental and eco physiological variables but also to their variances or other measures of variability. We use Mediterranean plant communities as examples, because they present characteristic large seasonal and inter annual fluctuations in water and nutrient availabilities, along an episodic-constant gradient, and because the plant responses include a number of syndromes coupled to this gradient.

  13. Insects in fluctuating thermal environments.

    Science.gov (United States)

    Colinet, Hervé; Sinclair, Brent J; Vernon, Philippe; Renault, David

    2015-01-07

    All climate change scenarios predict an increase in both global temperature means and the magnitude of seasonal and diel temperature variation. The nonlinear relationship between temperature and biological processes means that fluctuating temperatures lead to physiological, life history, and ecological consequences for ectothermic insects that diverge from those predicted from constant temperatures. Fluctuating temperatures that remain within permissive temperature ranges generally improve performance. By contrast, those which extend to stressful temperatures may have either positive impacts, allowing repair of damage accrued during exposure to thermal extremes, or negative impacts from cumulative damage during successive exposures. We discuss the mechanisms underlying these differing effects. Fluctuating temperatures could be used to enhance or weaken insects in applied rearing programs, and any prediction of insect performance in the field-including models of climate change or population performance-must account for the effect of fluctuating temperatures.

  14. Nonequilibrium quantum fluctuations of work.

    Science.gov (United States)

    Allahverdyan, A E

    2014-09-01

    The concept of work is basic for statistical thermodynamics. To gain a fuller understanding of work and its (quantum) features, it needs to be represented as an average of a fluctuating quantity. Here I focus on the work done between two moments of time for a thermally isolated quantum system driven by a time-dependent Hamiltonian. I formulate two natural conditions needed for the fluctuating work to be physically meaningful for a system that starts its evolution from a nonequilibrium state. The existing definitions do not satisfy these conditions due to issues that are traced back to noncommutativity. I propose a definition of fluctuating work that is free of previous drawbacks and that applies for a wide class of nonequilibrium initial states. It allows the deduction of a generalized work-fluctuation theorem that applies for an arbitrary (out-of-equilibrium) initial state.

  15. Quantum fluctuations in insulating ferroelectrics

    International Nuclear Information System (INIS)

    Riseborough, Peter S.

    2010-01-01

    Graphical abstract: It has been proposed that in a ferroelectric insulator, an applied magnetic field may couple the transverse phonon modes and produce left and right circularly polarized phonon modes which are no longer degenerate. We quantize the theory and examine the effects of quantal fluctuations. In particular, we show that the zero point fluctuations result in a large diamagnetic contribution to the magnetic susceptibility. - Abstract: It has been proposed that in a ferroelectric insulator, an applied magnetic field may couple the transverse phonon modes and produce left and right circularly polarized phonon modes which are no longer degenerate. We quantize the theory and examine the effects of quantal fluctuations. In particular, we show that the zero-point fluctuations result in a large diamagnetic contribution to the magnetic susceptibility.

  16. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, Élisabeth

    2011-01-21

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations of the velocities of spheres to increase with the size of the container, whereas experiments found no such variation. Two ideas have increased our understanding. First, the correlation length of the velocity fluctuations was found experimentally to be 20 interparticle separations. Second, in dilute suspensions, a vertical variation in the concentration due to the spreading of the front with the clear fluid can inhibit the velocity fluctuations. In a very dilute regime, a homogeneous suspension of fibers suffers a spontaneous instability in which fast descending fiber-rich columns are separated by rising fiber-sparse columns. In a semidilute regime, the settling is hindered, more so than for spheres. © 2011 by Annual Reviews. All rights reserved.

  17. Principle of minimal work fluctuations.

    Science.gov (United States)

    Xiao, Gaoyang; Gong, Jiangbin

    2015-08-01

    Understanding and manipulating work fluctuations in microscale and nanoscale systems are of both fundamental and practical interest. For example, in considering the Jarzynski equality 〈e-βW〉=e-βΔF, a change in the fluctuations of e-βW may impact how rapidly the statistical average of e-βW converges towards the theoretical value e-βΔF, where W is the work, β is the inverse temperature, and ΔF is the free energy difference between two equilibrium states. Motivated by our previous study aiming at the suppression of work fluctuations, here we obtain a principle of minimal work fluctuations. In brief, adiabatic processes as treated in quantum and classical adiabatic theorems yield the minimal fluctuations in e-βW. In the quantum domain, if a system initially prepared at thermal equilibrium is subjected to a work protocol but isolated from a bath during the time evolution, then a quantum adiabatic process without energy level crossing (or an assisted adiabatic process reaching the same final states as in a conventional adiabatic process) yields the minimal fluctuations in e-βW, where W is the quantum work defined by two energy measurements at the beginning and at the end of the process. In the classical domain where the classical work protocol is realizable by an adiabatic process, then the classical adiabatic process also yields the minimal fluctuations in e-βW. Numerical experiments based on a Landau-Zener process confirm our theory in the quantum domain, and our theory in the classical domain explains our previous numerical findings regarding the suppression of classical work fluctuations [G. Y. Xiao and J. B. Gong, Phys. Rev. E 90, 052132 (2014)].

  18. Model of cancer growth affected by irradiation. Effect of fluctuating intensity of the dose

    International Nuclear Information System (INIS)

    Gudowska-Nowak, E.

    1984-01-01

    The behaviour of a biological model system which describes the growth of a cancer cell population in the presence of external irradiation is studied. The effect of randomly fluctuating source of radiation is analysed and its influence on cancer cell extinction is presented. The main stress is put on the biological significance of random fluctuations which seem to favour rejection of a tumor. (author)

  19. Continuum random-phase approximation study of the incoherent μ--e- conversion rate and its spurious 1- admixture

    International Nuclear Information System (INIS)

    Papakonstantinou, P.; Wambach, J.; Kosmas, T.S.; Faessler, A.

    2006-01-01

    The incoherent transition strength of the exotic μ - -e - conversion in the 208 Pb nucleus is investigated by utilizing the continuum random-phase-approximation method, appropriate for the evaluation of the rate that goes to the continuum of the nuclear spectrum. We find that the contribution of resonances lying high in the continuum is not negligible. Special attention is paid to the detailed study of the pronounced 1 - contribution that according to previous calculations, dominates the overall incoherent rate in about all the nuclear targets. The spurious center-of-mass admixture to the partial rate originating from the 1 - excitations is explored, and its elimination is performed by correcting properly the dipole operators. The results found this way show that the greatest portion of the total 1 - contribution to the incoherent rate is spurious

  20. ARTIFICIAL INCOHERENT SPECKLES ENABLE PRECISION ASTROMETRY AND PHOTOMETRY IN HIGH-CONTRAST IMAGING

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, N.; Guyon, O.; Pathak, P.; Kudo, T. [National Astronomical Observatory of Japan, Subaru Telescope, 650 North A’Ohoku Place, Hilo, HI, 96720 (United States); Martinache, F. [Observatoire de la Cote d’Azur, Boulevard de l’Observatoire, F-06304 Nice (France); Hagelberg, J., E-mail: jovanovic.nem@gmail.com [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2015-11-10

    State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments are constantly improving the contrast detection limit for companions at ever-closer separations from the host star. In order to constrain their properties and, ultimately, compositions, it is important to precisely determine orbital parameters and contrasts with respect to the stars they orbit. This can be difficult in the post-coronagraphic image plane, as by definition the central star has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in the adaptive optics system of the Subaru Coronagraphic Extreme Adaptive Optics system to generate a field of speckles for the purposes of calibration. Speckles can be placed up to 22.5 λ/D from the star, with any position angle, brightness, and abundance required. Most importantly, we show that a fast modulation of the added speckle phase, between 0 and π, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitatively show for the first time that this incoherence, in turn, increases the robustness and stability of the adaptive speckles, which will improve the precision of astrometric and photometric calibration procedures. This technique will be valuable for high-contrast imaging observations with imagers and integral field spectrographs alike.

  1. Ground clutter cancellation in incoherent radars: solutions for EISCAT Svalbard radar

    Directory of Open Access Journals (Sweden)

    T. Turunen

    2000-09-01

    Full Text Available Incoherent scatter radars measure ionosphere parameters using modified Thomson scatter from free electrons in the target (see e.g. Hagfors, 1997. The integrated cross section of the ionospheric scatterers is extremely small and the measurements can easily be disturbed by signals returned by unwanted targets. Ground clutter signals, entering via the antenna side lobes, can render measurements at the nearest target ranges totally impossible. The EISCAT Svalbard Radar (ESR, which started measurements in 1996, suffers from severe ground clutter and the ionosphere cannot be measured in any simple manner at ranges less than about 120–150 km, depending on the modulation employed. If the target and clutter signals have different, and clearly identifiable, properties then, in principle, there are always ways to eliminate the clutter. In incoherent scatter measurements, differences in the coherence times of the wanted and unwanted signals can be used for clutter cancellation. The clutter cancellation must be applied to all modulations, usually alternating codes in modern experiments, used for shorter ranges. Excellent results have been obtained at the ESR using a simple pulse-to-pulse clutter subtraction method, but there are also other possibilities.Key words: Radio science (ionospheric physics; signal processing; instruments and techniques

  2. Direct, coherent and incoherent intermediate state tunneling and scanning tunnel microscopy (STM)

    International Nuclear Information System (INIS)

    Halbritter, J.

    1997-01-01

    Theory and experiment in tunneling are still qualitative in nature, which hold true also for the latest developments in direct-, resonant-, coherent- and incoherent-tunneling. Those tunnel processes have recently branched out of the field of ''solid state tunnel junctions'' into the fields of scanning tunnel microscopy (STM), single electron tunneling (SET) and semiconducting resonant tunnel structures (RTS). All these fields have promoted the understanding of tunneling in different ways reaching from the effect of coherence, of incoherence and of charging in tunneling, to spin flip or inelastic effects. STM allows not only the accurate measurements of the tunnel current and its voltage dependence but, more importantly, the easy quantification via the (quantum) tunnel channel conductance and the distance dependence. This new degree of freedom entering exponentially the tunnel current allows an unique identification of individual tunnel channels and their quantification. In STM measurements large tunnel currents are observed for large distances d > 1 nm explainable by intermediate state tunneling. Direct tunneling with its reduced tunnel time and reduced off-site Coulomb charging bridges distances below 1 nm, only. The effective charge transfer process with its larger off-site and on-site charging at intermediate states dominates tunnel transfer in STM, biology and chemistry over distances in the nm-range. Intermediates state tunneling becomes variable range hopping conduction for distances larger than d > 2 nm, for larger densities of intermediate states n 1 (ε) and for larger temperatures T or voltages U, still allowing high resolution imaging

  3. First E- and D-region incoherent scatter spectra observed over Jicamarca

    Directory of Open Access Journals (Sweden)

    J. L. Chau

    2006-07-01

    Full Text Available We present here the first Jicamarca observations of incoherent scatter radar (ISR spectra detected from E- and D-region altitudes. In the past such observations have not been possible at Jicamarca due a combined effect of strong equatorial electrojet (EEJ clutter and hardware limitations in the receiving system. The observations presented here were made during weak EEJ conditions (i.e., almost zero zonal electric field using an improved digital receiving system with a wide dynamic range and a high data throughput. The observed ISR spectra from E- and D-region altitudes are, as expected, narrow and get even narrower with decreasing altitude due to increasing ion-neutral collision frequencies. Therefore, it was possible to obtain accurate spectral measurements using a pulse-to-pulse data analysis. At lower altitudes in the D-region where signal correlation times are relatively long we used coherent integration to improve the signal-to-noise ratio of the collected data samples. The spectral estimates were fitted using a standard incoherent scatter (IS spectral model between 87 and 120 km, and a Lorentzian function below 110 km. Our preliminary estimates of temperature and ion-neutral collisions frequencies above 87 km are in good agreement with the MSISE-90 model. Below 87 km, the measured spectral widths are larger than expected, causing an overestimation of the temperatures, most likely due to spectral distortions caused by atmospheric turbulence.

  4. Loss of incoherence and determination of coupling constants in quantum gravity

    International Nuclear Information System (INIS)

    Giddings, S.B.; Strominger, A.

    1988-01-01

    The wave function of an interacting 'family' of one large 'parent' and many Planck-sized 'baby' universes is computed in a semiclassical approximation using an adaptation of Hartle-Hawking initial conditions. A recently discovered gravitational instanton which exists for general relativity coupled to axions is employed. The outcome of a single experiment in the parent universe is in general described by a mixed state, even if the initial state is pure. However, a sequence of measurements rapidly collapses the wave function of the family of universes into one of an infinite number of 'coherent' states for which quantum incoherence is not observed in the parent universe. This provides a concrete illustration of an unexpected phenomena whose existence has been argued for on quite general grounds by Coleman: Quantum incoherence due to information loss to baby universes is not experimentally observable. We further argue that all coupling constants governing dynamics in the parent universe depend on the parameters describing the particular coherent state into which the family wave function collapses. In particular, generically terms that violate any global symmetries will be induced in the effective action for the parent universe. These last results have much broader applicability than our specific model. (orig.)

  5. Structure and motion of junctions between coherent and incoherent twin boundaries in copper

    Energy Technology Data Exchange (ETDEWEB)

    Brown, J.A. [Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States); Ghoniem, N.M., E-mail: ghoniem@ucla.edu [Mechanical and Aerospace Engineering, University of California, Los Angeles, CA 90095 (United States)

    2009-09-15

    The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal annealing are investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent {Sigma}=3[110](112) twin boundary (ITB), pinned between two {Sigma}=3[110](111) twin boundaries, is determined. A three-dimensional structural model is described for the junction between intersecting coherent and incoherent twin boundaries, and migration velocities are calculated under thermal annealing conditions. It is shown that the coherent twin boundary (CTB)/ITB junction results in breaking the crystal symmetry by creation of either an edge dislocation or a mixed (edge/screw) at the intersection. These two types of defects can lead to pronounced differences in the observed migration (and hence annealing) rates of ICT/CTB junctions. The annealing rate resulting from the migration of ITBs with a mixed dislocation is found to be more than twice that of the edge dislocation. The mechanism of ITB motion is shown to be governed by successive kink-like motion of neighboring atomic columns, each of which is shifted by 1/4[1 1 0], followed by structural relaxation to accommodate boundary motion.

  6. Structure and motion of junctions between coherent and incoherent twin boundaries in copper

    International Nuclear Information System (INIS)

    Brown, J.A.; Ghoniem, N.M.

    2009-01-01

    The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal annealing are investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent Σ=3[110](112) twin boundary (ITB), pinned between two Σ=3[110](111) twin boundaries, is determined. A three-dimensional structural model is described for the junction between intersecting coherent and incoherent twin boundaries, and migration velocities are calculated under thermal annealing conditions. It is shown that the coherent twin boundary (CTB)/ITB junction results in breaking the crystal symmetry by creation of either an edge dislocation or a mixed (edge/screw) at the intersection. These two types of defects can lead to pronounced differences in the observed migration (and hence annealing) rates of ICT/CTB junctions. The annealing rate resulting from the migration of ITBs with a mixed dislocation is found to be more than twice that of the edge dislocation. The mechanism of ITB motion is shown to be governed by successive kink-like motion of neighboring atomic columns, each of which is shifted by 1/4[1 1 0], followed by structural relaxation to accommodate boundary motion.

  7. Tunable and broadband microwave frequency combs based on a semiconductor laser with incoherent optical feedback

    International Nuclear Information System (INIS)

    Zhao Mao-Rong; Wu Zheng-Mao; Deng Tao; Zhou Zhen-Li; Xia Guang-Qiong

    2015-01-01

    Based on a semiconductor laser (SL) with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs (MFCs) is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing (or repetition frequency) of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented. (paper)

  8. Occupational applications of ultraviolet radiation

    International Nuclear Information System (INIS)

    Eriksen, P.

    1987-01-01

    A large population of workers are exposed to ultraviolet radiation in various occupational environments which often necessitates protection. Since ultraviolet radiation may create other environmental problems an occupational hazard- and protection evaluation can be complicated. Threshold Limit Values adopted by the American Conference of Governmental Industrial Hygienists (ACGIH) on ultraviolet radiation are used in most countries as guidelines for risk assessment and control measures. This review addresses the levels of ultraviolet radiation met in occupational environments, its measurement and evaluation, and discusses different protection methods. Ultraviolet lasers are beginning to find their way into industrial processes but are still limited in number and they will not be covered here. Emphasis is on broad band incoherent radiation in high risk environments such as welding, and on the evaluation of protective eyewear, see-through curtains and plastics. Other occupational risks associated with the emission of ultraviolet radiation are discussed

  9. Rights versus labour privileges for ionizing radiation exposure activities

    International Nuclear Information System (INIS)

    Borges, Jose Carlos

    1996-01-01

    The present panorama of brazilian legislation concerning activities in which (may) occurs exposure to ionizing radiations, involves several incoherencies and privileges, as a consequence of legal rights generated from labor principles which have no social or scientific embasement. In this study, several legal labor topics are analysed and a new doutrinary context is proposed. (author)

  10. Quantum-gravity fluctuations and the black-hole temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)

    2015-05-15

    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum. (orig.)

  11. Quantum-gravity fluctuations and the black-hole temperature

    International Nuclear Information System (INIS)

    Hod, Shahar

    2015-01-01

    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum. (orig.)

  12. Interaction between a dark spot and a two-dimensional nonlinear photonic lattice with fully incoherent white light

    International Nuclear Information System (INIS)

    Liu, Zhaohong; Liu, Simin; Guo, Ru; Song, Tao; Zhu, Nan

    2007-01-01

    We study experimentally the interaction of a dark spot with a nonlinear photonic lattice with fully incoherent white light emitted from an incandescent bulb in the self-defocussing photovoltaic media when the dark spot is aimed at different positions of lattices with different lattice spacing. In this case a host of novel phenomena is demonstrated, including dark spot induced lattice dislocation-deformation, the annihilation of the dark spot and so on. Results demonstrate that the interaction between incoherent dark spot and photonic lattice is always attraction and the large-spacing photonic lattice is analogous to the continuous medium

  13. All-fiber incoherent frequency-to-time mapping method for microwave signal generation with baseband transmission and multicasting support

    DEFF Research Database (Denmark)

    Company Torres, Victor; Tafur Monroy, Idelfonso; Lancis, Jesus

    2008-01-01

    We present a proof-of-principle experiment for achieving simultaneous distribution of baseband radio-frequency data and up-conversion with broadcasting support over a passive optical network. The technique is based on an incoherent frequency-to-time mapping method for pulse shaping. Specifically...... resembles the shape of the incoherent source. The photodetected signal contains both the baseband data and an up-frequency converted copy with central wavelength for the microwave carrier into the ultra-wideband range and tuning capability by selection of the fiber length. (c) 2008 Elsevier B.V. All rights...

  14. Measurement of differential incoherent scattering cross-sections of 145 keV photons from K-shell electrons

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, V B; Ghumman, B S [Punjabi Univ., Patiala (India). Dept. of Physics

    1980-06-01

    Differential cross-sections for incoherent scattering of 145 keV photons from K-shell electrons of tin, silver and molybdenum have been measured at 110deg to investigate the effect of electron binding on differential cross-sections in the low energy region. The incoherent scattered photons are selected in coincidence with X-rays which follow the vacancies caused by the ejection of the electrons. NaI(Tl) scintillators are used for the detection of scattered photons and emitted X-rays. The experimental results are compared with the available theoretical data.

  15. Influence of Fano interference and incoherent processes on optical bistability in a four-level quantum dot nanostructure

    International Nuclear Information System (INIS)

    Hossein Asadpour, Seyyed; Solookinejad, G; Panahi, M; Ahmadi Sangachin, E

    2016-01-01

    Role of Fano interference and incoherent pumping field on optical bistability in a four-level designed InGaN/GaN quantum dot nanostructure embedded in a unidirectional ring cavity are analyzed. It is found that intensity threshold of optical bistability can be manipulated by Fano interference. It is shown that incoherent pumping fields make the threshold of optical bistability behave differently by Fano interference. Moreover, in the presence of Fano interference the medium becomes phase-dependent. Therefore, the relative phase of applied fields can affect the behaviors of optical bistability and intensity threshold can be controlled easily. (paper)

  16. Fluctuation analysis of rotational spectra

    International Nuclear Information System (INIS)

    Doessing, T.; Bracco, A.; Broglia, R.A.; Matsuo, M.

    1996-01-01

    The compound state rotational degree of freedom is ''damped'' in the sense that the electric quadrupole decay of a single quantum state with angular momentum I exhibits a spectrum of final states all having spin I-2. In actual experiments, the cascade of γ-rays associated with each of the members of the ensemble of compound nuclei uses each of the ''discrete'' transitions many more times than the ''continuum'' transitions. Relatively large and small fluctuations in the recorded coincidence spectrum ensue, respectively. The analysis of the fluctuations will be shown to be instrumental to gain insight into the phenomenon of rotational damping. For this purpose, two- and higher-fold coincidence spectra emitted from rotating nuclei are analyzed with respect to the count fluctuations. The coincidences from consecutive γ-rays emitted from discrete rotational bands generate ridges in the E γ1 .E γ2 spectrum, and the fluctuation analysis of the ridges is based upon the ansatz of a random selection of transition energies from band to band. This ansatz is supported by a cranked mean-field calculation for the nucleus 168 Yb, as well as by analyzing resolved bands in 168 Yb and its neighbors. The fluctuation analysis of the central valley (E γ1 =E γ2 ) is based upon the ansatz of fluctuations in the intensity of the transitions of Porter-Thomas type superposed on a smooth spectrum of transition energies. This ansatz is again supported by a mixed-band calculation. The mathematical treatment of count fluctuations is formulated in general (orig.)

  17. Rapid Fluctuations of Water Maser Emission in VY Canis Majoris

    Science.gov (United States)

    Zheng, Xing Wu; Scalise, Eugenio, Jr.; Han, Fu

    1998-11-01

    We report the observational results of short timescale monitoring of the 22 GHz water maser emission in VY CMa. A quasi-sinusoidal fluctuation has been detected with the relative flux intensity change of 20%-25% and a period of 10.3 day for two dominant features. This detected variability appears to be superimposed on the normal maser lines. We cannot easily explain the rapid fluctuation with the variation of the radiative input or the strong interstellar scintillation along the line of sight. The variation may be caused by the periodic shock.

  18. Thermodynamic Geometry and Hawking Radiation

    CERN Document Server

    Bellucci, S

    2010-01-01

    This work explores the role of thermodynamic fluctuations in the two parameter Hawking radiating black hole configurations. The system is characterized by an ensemble of arbitrary mass and radiation frequency of the black holes. In the due course of the Hawking radiations, we find that the intrinsic geometric description exhibits an intriguing set of exact pair correction functions and global correlation lengths. We investigate the nature of the constant amplitude radiation and find that it's not stable under fluctuations of the mass and frequency. Subsequently, the consideration of the York model decreasing amplitude radiation demonstrates that thermodynamic fluctuations are globally stable in the small frequency region. In connection with quantum gravity refinements, we take an account of the logarithmic correction into the constant amplitude and York amplitude over the Hawking radiation. In both considerations, we notice that the nature of the possible parametric fluctuations may precisely be ascertained w...

  19. Topics in fluctuating nonlinear hydrodynamics

    International Nuclear Information System (INIS)

    Milner, S.T.

    1986-01-01

    Models of fluctuating nonlinear hydrodynamics have enjoyed much success in explaining the effect of long-wavelength fluctuations in diverse hydrodynamic systems. This thesis explores two such problems; in both, the body of hydrodynamic assumptions powerfully constrains the predictions of a well-posed theory. The effects of layer fluctuations in smectic-A liquid crystals are first examined. The static theory (introduced by Grinstein and Pelcovits) is reviewed. Ward identities, resulting from the arbitrariness of the layering direction, are derived and exploited. The static results motivate an examination of dynamic fluctuation effects. A new sound-damping experiment is proposed that would probe singular dependence of viscosities on applied stress. A theory of Procaccia and Gitterman that reaction rates of chemically reacting binary mixtures are drastically reduced near their thermodynamic critical points is analyzed. Hydrodynamic arguments and Van Hove theory are applied, concluding that the PG idea is drastically slowed, and spatially varying composition fluctuations are at best slowed down over a narrow range of wavenumbers

  20. Electric Field Fluctuations in Water

    Science.gov (United States)

    Thorpe, Dayton; Limmer, David; Chandler, David

    2013-03-01

    Charge transfer in solution, such as autoionization and ion pair dissociation in water, is governed by rare electric field fluctuations of the solvent. Knowing the statistics of such fluctuations can help explain the dynamics of these rare events. Trajectories short enough to be tractable by computer simulation are virtually certain not to sample the large fluctuations that promote rare events. Here, we employ importance sampling techniques with classical molecular dynamics simulations of liquid water to study statistics of electric field fluctuations far from their means. We find that the distributions of electric fields located on individual water molecules are not in general gaussian. Near the mean this non-gaussianity is due to the internal charge distribution of the water molecule. Further from the mean, however, there is a previously unreported Bjerrum-like defect that stabilizes certain large fluctuations out of equilibrium. As expected, differences in electric fields acting between molecules are gaussian to a remarkable degree. By studying these differences, though, we are able to determine what configurations result not only in large electric fields, but also in electric fields with long spatial correlations that may be needed to promote charge separation.

  1. Multiscale fluctuations in nuclear response

    International Nuclear Information System (INIS)

    Lacroix, D.; Chomaz, Ph.

    1999-01-01

    The nuclear collective response is investigated in the framework of a doorway picture in which the spreading width of the collective emotion is described as a coupling to more and more complex configurations. It is shown that this coupling induces fluctuations of the observed strength. In the case of a hierarchy of overlapping decay channels, Ericson fluctuations are observed at different scales. Methods for extracting these scales and the related lifetimes are discussed. Finally, it is shown that the coupling of different states at one level of complexity to some common decay channels at the next level, may produce interference-like patterns in the nuclear response. This quantum effect leads to anew type of fluctuations with a typical width related to the level spacing. (author)

  2. Fluctuation relations for anomalous dynamics

    International Nuclear Information System (INIS)

    Chechkin, A V; Klages, R

    2009-01-01

    We consider work fluctuation relations (FRs) for generic types of dynamics generating anomalous diffusion: Lévy flights, long-correlated Gaussian processes and time-fractional kinetics. By combining Langevin and kinetic approaches we calculate the probability distributions of mechanical and thermodynamical work in two paradigmatic nonequilibrium situations, respectively: a particle subject to a constant force and a particle in a harmonic potential dragged by a constant force. We check the transient FR for two models exhibiting superdiffusion, where a fluctuation-dissipation relation does not exist, and for two other models displaying subdiffusion, where there is a fluctuation-dissipation relation. In the two former cases the conventional transient FR is not recovered, whereas in the latter two it holds either exactly or in the long-time limit. (letter)

  3. Fluctuations in the multiparticle dynamics

    International Nuclear Information System (INIS)

    Bozek, P.; Ploszajczak, M.

    1993-01-01

    The appearance and properties of intermittent fluctuations in physical systems, in particular the formation of rare structures in transport phenomena are discussed. The distribution of fluctuations approaches a limiting log-normal statistical distribution. The log-normal distribution is introduced as a simple parametrization of the energy fluctuations leading to the subthreshold production of particles in nuclear collisions, and it is shown that it fits all available data both for total π 0 production cross section as well as the π 0 kinetic energy spectra for E/A < 90 MeV. It is suggested that the same universal distribution should also describe the subthreshold production of other hadrons like η and K. (author) 36 refs., 11 figs

  4. Multiscale fluctuations in nuclear response

    Energy Technology Data Exchange (ETDEWEB)

    Lacroix, D.; Chomaz, Ph

    1999-01-01

    The nuclear collective response is investigated in the framework of a doorway picture in which the spreading width of the collective emotion is described as a coupling to more and more complex configurations. It is shown that this coupling induces fluctuations of the observed strength. In the case of a hierarchy of overlapping decay channels, Ericson fluctuations are observed at different scales. Methods for extracting these scales and the related lifetimes are discussed. Finally, it is shown that the coupling of different states at one level of complexity to some common decay channels at the next level, may produce interference-like patterns in the nuclear response. This quantum effect leads to anew type of fluctuations with a typical width related to the level spacing. (author) 25 refs.

  5. Phase space fluctuations and dynamics of fluctuations of collective variables

    Energy Technology Data Exchange (ETDEWEB)

    Benhassine, B.; Farine, M.; Idier, D.; Remaud, B.; Sebille, F. (Lab. de Physique Nucleaire, IN2P3/CNRS, 44 - Nantes (France) Nantes Univ., 44 (France)); Hernandez, E.S. (Dept. de Fisica, Ciudad Universitaria, Buenos Aires (Argentina))

    1992-08-03

    Within the framework of theoretical approaches based on stochastic transport equation of one-body distribution function, a numerical treatment of the fluctuations of collective observables is studied and checked in comparison with analytical results either at equilibrium or close to it. (orig.).

  6. Phase space fluctuations and dynamics of fluctuations of collective variables

    International Nuclear Information System (INIS)

    Benhassine, B.; Farine, M.; Idier, D.; Remaud, B.; Sebille, F.; Hernandez, E.S.

    1992-01-01

    Within the framework of theoretical approaches based on stochastic transport equation of one-body distribution function, a numerical treatment of the fluctuations of collective observables is studied and checked in comparison with analytical results either at equilibrium or close to it. (orig.)

  7. Entropic Repulsion Between Fluctuating Surfaces

    Science.gov (United States)

    Janke, W.

    The statistical mechanics of fluctuating surfaces plays an important role in a variety of physical systems, ranging from biological membranes to world sheets of strings in theories of fundamental interactions. In many applications it is a good approximation to assume that the surfaces possess no tension. Their statistical properties are then governed by curvature energies only, which allow for gigantic out-of-plane undulations. These fluctuations are the “entropic” origin of long-range repulsive forces in layered surface systems. Theoretical estimates of these forces for simple model surfaces are surveyed and compared with recent Monte Carlo simulations.

  8. Origin of cosmological density fluctuations

    International Nuclear Information System (INIS)

    Carr, B.J.

    1984-11-01

    The density fluctuations required to explain the large-scale cosmological structure may have arisen spontaneously as a result of a phase transition in the early Universe. There are several ways in which such fluctuations may have ben produced, and they could have a variety of spectra, so one should not necessarily expect all features of the large-scale structure to derive from a simple power law spectrum. Some features may even result from astrophysical amplification mechanisms rather than gravitational instability. 128 references

  9. Daytime and Nighttime Neutral Wind and Temperature Measurements from Incoherent Scatter Radar at 300 KM over Arecibo.

    Science.gov (United States)

    1985-12-01

    Incoherent *scatter observations and their interpretation, 3. Atmos. Tarr. Phys., 34, 351-364, 1972. Bohnk&,R., and Harper,R., Vector measurements of F...equatorial F-region, 3. Atmos. Terr. Phys., 39, 1159-1168, 1977. Rishbeth, H., Ganguly,S., Walker,3.C., Feild -aligned and field-perpendicular velocities

  10. Excitation decay due to incoherent energy transfer : A comparative study by means of an exact density expansion

    NARCIS (Netherlands)

    Knoester, J.; Himbergen, J.E. Van

    1984-01-01

    In this paper we consider a system of identical, randomly distributed donors, between which incoherent energy transfer takes place, described by coupled rate equations. It is proved, that the well-known diagrammatic series expansion of Gochanour, Andersen, and Fayer for the self-energy, while not an

  11. The effect of, within the sphere confined, particle diffusion on the line shape of incoherent cold neutron scattering spectra

    International Nuclear Information System (INIS)

    Cvikl, B.; Dahlborg, U.; Calvo-Dahlborg, M.

    1999-01-01

    Based upon the model of particles diffusion within the sphere of partially absorbing boundaries, the possibilities of the detection, by the incoherent cold neutron scattering method, of particle precipitation on the boundary walls, has been investigated. The calculated scattering law as a function of the boundary absorption properties exhibits distinct characteristic which might, under favorable conditions, make such an experimental attempt feasible.(author)

  12. Simulation of spatially varying ground motions including incoherence, wave‐passage and differential site‐response effects

    DEFF Research Database (Denmark)

    Konakli, Katerina; Der Kiureghian, Armen

    2012-01-01

    A method is presented for simulating arrays of spatially varying ground motions, incorporating the effects of incoherence, wave passage, and differential site response. Non‐stationarity is accounted for by considering the motions as consisting of stationary segments. Two approaches are developed....

  13. Electron and ion temperatures: a comparison of ground-based incoherent scatter and AE-C satellite measurements

    International Nuclear Information System (INIS)

    Benson, R.F.; Bauer, P.; Brace, L.H.; Carlson, H.C.; Hagen, J.; Hanson, W.B.; Hoegy, W.R.; Torr, M.R.; Wickwar, V.B.

    1977-01-01

    The Atmosphere Exploere-C satellite (AE-C) is uniquely suited for correlative studies with ground-based stations because its on-board propulsion system enables a desired ground station overflight condition to be maintained for a period of several weeks. It also provides the first low-altitude (below 260 km) comparison of satellite and incoherent scatter electron and ion temperatures. More than 40 comparisons of remote and in situ measurements were made by using data from AE-C and four incoherent scatter stations (Arecibo, Chatanika, Millstone Hill, and St. Santin). The results indicate very good agreement between satellite and ground measurements of the ion temperature, the average satellite retarding potential analyzer temperatures differing from the average incoherent scatter temperatures by -2% at St. Santin, +3% at Millstone Hill, and +2% at Arecibo. The electron temperatures also agree well, the average satellite temperatures exceeding the average incoherent scatter temperatures by 3% at St. Santin, 2% at Arecibo, and 11% at Millstone Hill. Several temperature comparisons were made between AE-C and Chatanika. In spite of the highly variable ionosphere often encountered at this high-latitude location, good agreement was obtained between the in situ and remote measurements of electron and ion temperatures. Longitudinal variations are found to be very important in the comparisons of electron temperature in some locations. The agreement between the electron temperatures is considerably better than that found in some earlier comparisons involving satellities at higher altitudes

  14. Probabilistic and deterministic soil structure interaction analysis including ground motion incoherency effects

    International Nuclear Information System (INIS)

    Elkhoraibi, T.; Hashemi, A.; Ostadan, F.

    2014-01-01

    Soil-structure interaction (SSI) is a major step for seismic design of massive and stiff structures typical of the nuclear facilities and civil infrastructures such as tunnels, underground stations, dams and lock head structures. Currently most SSI analyses are performed deterministically, incorporating limited range of variation in soil and structural properties and without consideration of the ground motion incoherency effects. This often leads to overestimation of the seismic response particularly the In-Structure-Response Spectra (ISRS) with significant impositions of design and equipment qualification costs, especially in the case of high-frequency sensitive equipment at stiff soil or rock sites. The reluctance to incorporate a more comprehensive probabilistic approach is mainly due to the fact that the computational cost of performing probabilistic SSI analysis even without incoherency function considerations has been prohibitive. As such, bounding deterministic approaches have been preferred by the industry and accepted by the regulatory agencies. However, given the recently available and growing computing capabilities, the need for a probabilistic-based approach to the SSI analysis is becoming clear with the advances in performance-based engineering and the utilization of fragility analysis in the decision making process whether by the owners or the regulatory agencies. This paper demonstrates the use of both probabilistic and deterministic SSI analysis techniques to identify important engineering demand parameters in the structure. A typical nuclear industry structure is used as an example for this study. The system is analyzed for two different site conditions: rock and deep soil. Both deterministic and probabilistic SSI analysis approaches are performed, using the program SASSI, with and without ground motion incoherency considerations. In both approaches, the analysis begins at the hard rock level using the low frequency and high frequency hard rock

  15. Errors due to random noise in velocity measurement using incoherent-scatter radar

    Directory of Open Access Journals (Sweden)

    P. J. S. Williams

    1996-12-01

    Full Text Available The random-noise errors involved in measuring the Doppler shift of an 'incoherent-scatter' spectrum are predicted theoretically for all values of Te/Ti from 1.0 to 3.0. After correction has been made for the effects of convolution during transmission and reception and the additional errors introduced by subtracting the average of the background gates, the rms errors can be expressed by a simple semi-empirical formula. The observed errors are determined from a comparison of simultaneous EISCAT measurements using an identical pulse code on several adjacent frequencies. The plot of observed versus predicted error has a slope of 0.991 and a correlation coefficient of 99.3%. The prediction also agrees well with the mean of the error distribution reported by the standard EISCAT analysis programme.

  16. A compact new incoherent Thomson scattering diagnostic for low-temperature plasma studies

    Science.gov (United States)

    Vincent, Benjamin; Tsikata, Sedina; Mazouffre, Stéphane; Minea, Tiberiu; Fils, Jérôme

    2018-05-01

    Incoherent Thomson scattering (ITS) has a long history of application for the determination of electron density and temperature in dense fusion plasmas, and in recent years, has been increasingly extended to studies in low-temperature plasma environments. In this work, the design and preliminary implementation of a new, sensitive and uniquely compact ITS platform known as Thomson scattering experiments for low temperature ion sources are described. Measurements have been performed on a hollow cathode plasma source, providing access to electron densities as low as 1016 m‑3 and electron temperatures of a few eV and below. This achievement has been made possible by the implementation of a narrow volume Bragg grating notch filter for the attenuation of stray light, a feature which guarantees compactness and reduced transmission losses in comparison to standard ITS platforms.

  17. Ray-optics cloaking devices for large objects in incoherent natural light

    Science.gov (United States)

    Chen, Hongsheng; Zheng, Bin; Shen, Lian; Wang, Huaping; Zhang, Xianmin; Zheludev, Nikolay I.; Zhang, Baile

    2013-10-01

    A cloak that can hide living creatures from sight is a common feature of mythology but still remains unrealized as a practical device. To preserve the wave phase, the previous cloaking solution proposed by Pendry and colleagues required transformation of the electromagnetic space around the hidden object in such a way that the rays bending around the object inside the cloak region have to travel faster than those passing it by. This difficult phase preservation requirement is the main obstacle for building a broadband polarization-insensitive cloak for large objects. Here we propose a simplified version of Pendry’s cloak by abolishing the requirement for phase preservation, as it is irrelevant for observation using incoherent natural light with human eyes, which are phase and polarization insensitive. This allows for a cloak design on large scales using commonly available materials. We successfully demonstrate the cloaking of living creatures, a cat and a fish, from the eye.

  18. Collective dynamics of populations of weakly correlated filaments of incoherent white light

    International Nuclear Information System (INIS)

    Guo, Jinxin; Sheridan, John T; Saravanamuttu, Kalaichelvi

    2013-01-01

    We examined the dynamics of two populations of self-trapped filaments of spatially and temporally incoherent white light. The populations consisted of (i) independent filaments generated through self-trapping of incandescent speckles, and (ii) co-dependent filaments created through modulation instability of a broad incandescent beam. Both filament populations were positionally stable in conditions where individual pairs of self-trapped beams interact strongly. Both also acquired significantly broad intensity distributions, which were independent of their parent optical fields; a small but persistent number of high-intensity filaments was identified in both cases. These studies provide accessible routes to weakly correlated ensembles, insight into their collective behaviour such as self-stabilization and self-selected intensity distributions, and reveal intriguing similarities between the dynamics of two populations of different origins. (paper)

  19. Incoherent dictionary learning for reducing crosstalk noise in least-squares reverse time migration

    Science.gov (United States)

    Wu, Juan; Bai, Min

    2018-05-01

    We propose to apply a novel incoherent dictionary learning (IDL) algorithm for regularizing the least-squares inversion in seismic imaging. The IDL is proposed to overcome the drawback of traditional dictionary learning algorithm in losing partial texture information. Firstly, the noisy image is divided into overlapped image patches, and some random patches are extracted for dictionary learning. Then, we apply the IDL technology to minimize the coherency between atoms during dictionary learning. Finally, the sparse representation problem is solved by a sparse coding algorithm, and image is restored by those sparse coefficients. By reducing the correlation among atoms, it is possible to preserve most of the small-scale features in the image while removing much of the long-wavelength noise. The application of the IDL method to regularization of seismic images from least-squares reverse time migration shows successful performance.

  20. Critical exponents of the transition from incoherence to partial oscillation death in the Winfree model

    International Nuclear Information System (INIS)

    Basnarkov, Lasko; Urumov, Viktor

    2009-01-01

    We consider an analytically solvable version of the Winfree model of synchronization of phase oscillators (proposed by Ariaratnam and Strogatz 2001 Phys. Rev. Lett. 86 4278). It is obtained that the transition from incoherence to a partial death state is characterized by third-order or higher phase transitions according to the Ehrenfest classification. The order of the transition depends on the shape of the distribution function for natural frequencies of oscillators in the vicinity of their lowest frequency. The corresponding critical exponents are found analytically and verified with numerical simulations of equations of motion. We also consider the generalized Winfree model with the interaction strength proportional to a power of the Kuramoto order parameter and find the domain where the critical exponent remains unchanged by this modification

  1. Incoherent feedforward control governs adaptation of activated ras in a eukaryotic chemotaxis pathway.

    Science.gov (United States)

    Takeda, Kosuke; Shao, Danying; Adler, Micha; Charest, Pascale G; Loomis, William F; Levine, Herbert; Groisman, Alex; Rappel, Wouter-Jan; Firtel, Richard A

    2012-01-03

    Adaptation in signaling systems, during which the output returns to a fixed baseline after a change in the input, often involves negative feedback loops and plays a crucial role in eukaryotic chemotaxis. We determined the dynamical response to a uniform change in chemoattractant concentration of a eukaryotic chemotaxis pathway immediately downstream from G protein-coupled receptors. The response of an activated Ras showed near-perfect adaptation, leading us to attempt to fit the results using mathematical models for the two possible simple network topologies that can provide perfect adaptation. Only the incoherent feedforward network accurately described the experimental results. This analysis revealed that adaptation in this Ras pathway is achieved through the proportional activation of upstream components and not through negative feedback loops. Furthermore, these results are consistent with a local excitation, global inhibition mechanism for gradient sensing, possibly with a Ras guanosine triphosphatase-activating protein acting as a global inhibitor.

  2. Enhancement of the incoherent scattering plasma lines due to precipitating protons and secondary electrons

    International Nuclear Information System (INIS)

    Bjoernaa, N.; Havnes, O.; Jensen, J.O.; Trulsen, J.

    1982-01-01

    Precipitating protons in the energy range 1-100 keV are regularly present in the auroral ionosphere. These protons will produce enhancements in the intensity of the upshifted plasma line of the incoherently scattered spectrum. Similarly, secondary electrons produced by the precipitating protons give rise to enhanced plasma line intensities. For a quantitative discussion of these effects an experimentally measured proton flux is adapted and the corresponding secondary electron flux calculated. These particle fluxes are then applied in connection with the EISCAT radar facility. Both fluxes give rise to enhancements of the order of 20. It is possible to separate between proton and electron contributions to the enhanced plasma lines for scattering heights above the source region of secondary electrons. (Auth.)

  3. Incoherent-scatter radar measurements of electric field and plasma in the auroral ionosphere

    International Nuclear Information System (INIS)

    Vondrak, R.

    1983-01-01

    This chapter summarizes Chatanika radar measurements of electric fields and currents, and their relation to E-region ionization and conductivity. Electric-field coupling between the ionosphere and magnetosphere and the relationship between field-aligned currents and meridional ionospheric currents are examined. Topics considered include the diurnal pattern of the ionization and electric field; electrical coupling between the ionosphere and magnetosphere; and the relationship between meridional currents and field-aligned currents. It is concluded that the incoherent-scatter radar technique has been developed into a powerful method for remotely measuring the electrical and thermal properties of the auroral ionospheric plasma, and that the usefulness of the radar measurements is greatly enhanced when combined with simultaneous satellite measurements

  4. A mixed incoherent feed-forward loop contributes to the regulation of bacterial photosynthesis genes.

    Science.gov (United States)

    Mank, Nils N; Berghoff, Bork A; Klug, Gabriele

    2013-03-01

    Living cells use a variety of regulatory network motifs for accurate gene expression in response to changes in their environment or during differentiation processes. In Rhodobacter sphaeroides, a complex regulatory network controls expression of photosynthesis genes to guarantee optimal energy supply on one hand and to avoid photooxidative stress on the other hand. Recently, we identified a mixed incoherent feed-forward loop comprising the transcription factor PrrA, the sRNA PcrZ and photosynthesis target genes as part of this regulatory network. This point-of-view provides a comparison to other described feed-forward loops and discusses the physiological relevance of PcrZ in more detail.

  5. Formation of incoherent deformation twin boundaries in a coarse-grained Al-7Mg alloy

    Science.gov (United States)

    Jin, S. B.; Zhang, K.; Bjørge, R.; Tao, N. R.; Marthinsen, K.; Lu, K.; Li, Y. J.

    2015-08-01

    Deformation twinning has rarely been observed in coarse grained Al and its alloys except under some extreme conditions such as ultrahigh deformation strain or strain rates. Here, we report that a significant amount of Σ3 deformation twins could be generated in a coarse-grained Al-7 Mg alloy by dynamic plastic deformation (DPD). A systematic investigation of the Σ3 boundaries shows that they are Σ3{112} type incoherent twin boundaries (ITBs). These ITBs have formed by gradual evolution from copious low-angle deformation bands through -twist Σ boundaries by lattice rotation. These findings provide an approach to generate deformation twin boundaries in high stacking fault energy metallic alloys. It is suggested that high solution content of Mg in the alloy and the special deformation mode of DPD played an important role in formation of the Σ and ITBs.

  6. Design, demonstration and analysis of a modified wavelength-correlating receiver for incoherent OCDMA system.

    Science.gov (United States)

    Zhou, Heng; Qiu, Kun; Wang, Leyang

    2011-03-28

    A novel wavelength-correlating receiver for incoherent Optical Code Division Multiple Access (OCDMA) system is proposed and demonstrated in this paper. Enabled by the wavelength conversion based scheme, the proposed receiver can support various code types including one-dimensional optical codes and time-spreading/wavelength-hopping two dimensional codes. Also, a synchronous detection scheme with time-to- wavelength based code acquisition is proposed, by which code acquisition time can be substantially reduced. Moreover, a novel data-validation methodology based on all-optical pulse-width monitoring is introduced for the wavelength-correlating receiver. Experimental demonstration of the new proposed receiver is presented and low bit error rate data-receiving is achieved without optical hard limiting and electronic power thresholding. For the first time, a detailed theoretical performance analysis specialized for the wavelength-correlating receiver is presented. Numerical results show that the overall performance of the proposed receiver prevails over conventional OCDMA receivers.

  7. Probabilistic and deterministic soil structure interaction analysis including ground motion incoherency effects

    Energy Technology Data Exchange (ETDEWEB)

    Elkhoraibi, T., E-mail: telkhora@bechtel.com; Hashemi, A.; Ostadan, F.

    2014-04-01

    Soil-structure interaction (SSI) is a major step for seismic design of massive and stiff structures typical of the nuclear facilities and civil infrastructures such as tunnels, underground stations, dams and lock head structures. Currently most SSI analyses are performed deterministically, incorporating limited range of variation in soil and structural properties and without consideration of the ground motion incoherency effects. This often leads to overestimation of the seismic response particularly the In-Structure-Response Spectra (ISRS) with significant impositions of design and equipment qualification costs, especially in the case of high-frequency sensitive equipment at stiff soil or rock sites. The reluctance to incorporate a more comprehensive probabilistic approach is mainly due to the fact that the computational cost of performing probabilistic SSI analysis even without incoherency function considerations has been prohibitive. As such, bounding deterministic approaches have been preferred by the industry and accepted by the regulatory agencies. However, given the recently available and growing computing capabilities, the need for a probabilistic-based approach to the SSI analysis is becoming clear with the advances in performance-based engineering and the utilization of fragility analysis in the decision making process whether by the owners or the regulatory agencies. This paper demonstrates the use of both probabilistic and deterministic SSI analysis techniques to identify important engineering demand parameters in the structure. A typical nuclear industry structure is used as an example for this study. The system is analyzed for two different site conditions: rock and deep soil. Both deterministic and probabilistic SSI analysis approaches are performed, using the program SASSI, with and without ground motion incoherency considerations. In both approaches, the analysis begins at the hard rock level using the low frequency and high frequency hard rock

  8. Optical information encryption based on incoherent superposition with the help of the QR code

    Science.gov (United States)

    Qin, Yi; Gong, Qiong

    2014-01-01

    In this paper, a novel optical information encryption approach is proposed with the help of QR code. This method is based on the concept of incoherent superposition which we introduce for the first time. The information to be encrypted is first transformed into the corresponding QR code, and thereafter the QR code is further encrypted into two phase only masks analytically by use of the intensity superposition of two diffraction wave fields. The proposed method has several advantages over the previous interference-based method, such as a higher security level, a better robustness against noise attack, a more relaxed work condition, and so on. Numerical simulation results and actual smartphone collected results are shown to validate our proposal.

  9. Unidirectional reflection and invisibility in nonlinear media with an incoherent nonlinearity

    Science.gov (United States)

    Mostafazadeh, Ali; Oflaz, Neslihan

    2017-11-01

    We give explicit criteria for the reflectionlessness, transparency, and invisibility of a finite-range potential in the presence of an incoherent (intensity-dependent) nonlinearity that is confined to the range of the potential. This allows us to conduct a systematic study of the effects of such a nonlinearity on a locally periodic class of finite-range potentials that display perturbative unidirectional invisibility. We use our general results to examine the effects of a weak Kerr nonlinearity on the behavior of these potentials and show that the presence of nonlinearity destroys the unidirectional invisibility of these potentials. If the strength of the Kerr nonlinearity is so weak that the first-order perturbation theory is reliable, the presence of nonlinearity does not affect the unidirectional reflectionlessness and transmission reciprocity of the potential. We show that the expected violation of the latter is a second order perturbative effect.

  10. Intravoxel incoherent motion (IVIM histogram biomarkers for prediction of neoadjuvant treatment response in breast cancer patients

    Directory of Open Access Journals (Sweden)

    Gene Y. Cho

    Full Text Available Objective: To examine the prognostic capabilities of intravoxel incoherent motion (IVIM metrics and their ability to predict response to neoadjuvant treatment (NAT. Additionally, to observe changes in IVIM metrics between pre- and post-treatment MRI. Methods: This IRB-approved, HIPAA-compliant retrospective study observed 31 breast cancer patients (32 lesions. Patients underwent standard bilateral breast MRI along with diffusion-weighted imaging before and after NAT. Six patients underwent an additional IVIM-MRI scan 12–14 weeks after initial scan and 2 cycles of treatment. In addition to apparent diffusion coefficients (ADC from monoexponential decay, IVIM mean values (tissue diffusivity Dt, perfusion fraction fp, and pseudodiffusivity Dp and histogram metrics were derived using a biexponential model. An additional filter identified voxels of highly vascular tumor tissue (VTT, excluding necrotic or normal tissue. Clinical data include histology of biopsy and clinical response to treatment through RECIST assessment. Comparisons of treatment response were made using Wilcoxon rank-sum tests. Results: Average, kurtosis, and skewness of pseudodiffusion Dp significantly differentiated RECIST responders from nonresponders. ADC and Dt values generally increased (∼70% and VTT% values generally decreased (∼20% post-treatment. Conclusion: Dp metrics showed prognostic capabilities; slow and heterogeneous pseudodiffusion offer poor prognosis. Baseline ADC/Dt parameters were not significant predictors of response. This work suggests that IVIM mean values and heterogeneity metrics may have prognostic value in the setting of breast cancer NAT. Keywords: Breast cancer, Diffusion weighted MRI, Intravoxel incoherent motion, Neoadjuvant treatment, Response evaluation criteria in solid tumors

  11. Variability of non-Gaussian diffusion MRI and intravoxel incoherent motion (IVIM) measurements in the breast.

    Science.gov (United States)

    Iima, Mami; Kataoka, Masako; Kanao, Shotaro; Kawai, Makiko; Onishi, Natsuko; Koyasu, Sho; Murata, Katsutoshi; Ohashi, Akane; Sakaguchi, Rena; Togashi, Kaori

    2018-01-01

    We prospectively examined the variability of non-Gaussian diffusion magnetic resonance imaging (MRI) and intravoxel incoherent motion (IVIM) measurements with different numbers of b-values and excitations in normal breast tissue and breast lesions. Thirteen volunteers and fourteen patients with breast lesions (seven malignant, eight benign; one patient had bilateral lesions) were recruited in this prospective study (approved by the Internal Review Board). Diffusion-weighted MRI was performed with 16 b-values (0-2500 s/mm2 with one number of excitations [NEX]) and five b-values (0-2500 s/mm2, 3 NEX), using a 3T breast MRI. Intravoxel incoherent motion (flowing blood volume fraction [fIVIM] and pseudodiffusion coefficient [D*]) and non-Gaussian diffusion (theoretical apparent diffusion coefficient [ADC] at b value of 0 sec/mm2 [ADC0] and kurtosis [K]) parameters were estimated from IVIM and Kurtosis models using 16 b-values, and synthetic apparent diffusion coefficient (sADC) values were obtained from two key b-values. The variabilities between and within subjects and between different diffusion acquisition methods were estimated. There were no statistical differences in ADC0, K, or sADC values between the different b-values or NEX. A good agreement of diffusion parameters was observed between 16 b-values (one NEX), five b-values (one NEX), and five b-values (three NEX) in normal breast tissue or breast lesions. Insufficient agreement was observed for IVIM parameters. There were no statistical differences in the non-Gaussian diffusion MRI estimated values obtained from a different number of b-values or excitations in normal breast tissue or breast lesions. These data suggest that a limited MRI protocol using a few b-values might be relevant in a clinical setting for the estimation of non-Gaussian diffusion MRI parameters in normal breast tissue and breast lesions.

  12. Seismic soil-structure interaction with consideration of spatial incoherence of seismic ground motions: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Wen S., E-mail: wen.tseng@rizzoassoc.com [Paul C. Rizzo Associates, Inc., Western Region, 2201 Broadway, Suite 400, Oakland, CA 94612 (United States); Lilhanand, Kiat; Hamasaki, Don; Garcia, Julio A. [Paul C. Rizzo Associates, Inc., Western Region, 2201 Broadway, Suite 400, Oakland, CA 94612 (United States); Srinivasan, Ram [AREVA, NP, Inc., 6399 San Ignacio Avenue, San Jose, CA 95119 (United States)

    2014-04-01

    This paper presents a case study of seismic soil-structure interaction (SSI) analysis with consideration of spatial incoherence of seismic input ground motions. The SSI analyses were performed using the SASSI computer program for the Auxiliary Control Building (ACB) structure of an existing nuclear power plant on a hard rock site located in the Center and Eastern United States (CEUS) region. The incoherent seismic input motions for the hard rock site used for the analyses were generated using the computer program INCOH that works together with SASSI. The objective of the analyses was to generate maximum seismic response parameters for assessment of potential impact of newly developed site-specific (ground motion) response spectra (SSRS) on the seismic design of the ACB and potential benefits that could be gained by considering spatial incoherence of seismic input motions. Maximum seismic response values for selected response parameters of interest were generated with both SSRS-compatible coherent and incoherent seismic input motions. Comparisons were made of the corresponding maximum response parameter values and in-structure (acceleration) response spectra (ISRS) generated for both the coherent and incoherent motion inputs. These comparisons indicate that, by incorporating incoherence of ground motions in the seismic input, the maximum response values reduces and the ISRS peak amplitudes in the high frequency range (>10 Hz) also reduce from the corresponding response values resulting from the coherent motion input. The amount of ISRS-amplitude reduction increases as the spectral frequency increases, as expected. Such reductions can be as much as 20–50%. This case study demonstrates that, for a CEUS hard rock site where relatively high high-frequency in the seismic input response spectra exist, consideration of spatial incoherence of input motions would result in substantial benefits in reducing the high-frequency seismic responses. Such benefits are especially

  13. Fluctuation effects in radiative capture to unstable final states: A test via the 89Y(rvec p,γ) reaction at Ep = 19.6 MeV

    International Nuclear Information System (INIS)

    Parker, W.E.; Chadwick, M.; Dietrich, F.S.

    1994-11-01

    The authors have developed an extended direct-semidirect (DSD) model for fast-nucleon capture to single-particle configurations that subsequently damp into the compound nucleus or (at sufficiently high excitation energies) escape into the continuum. The inclusion of final-state fluctuation effects is an important feature of this model. To test the model they have measured the spectra of gamma rays from approximately 10 MeV to the endpoint in the 89 Y(rvec P,γ) reaction with 19.6 MeV polarized protons from the TUNL tandem accelerator. Gamma spectra were measured with a pair of 25.4 cm x 25.4 cm anticoincidence-shielded NaI detectors at angles of 30 degree, 55 degree, 90 degree 125 degree and 150 degree with respect to the incident beam. The spectra show significant analyzing powers and forward peaking of the angular distributions. These features allow for the discrimination between compound processes and direct processes. Analyzing powers and fore-aft asymmetries were observed for gamma energies below those associated with direct-semidirect transitions to known bound final states. They have also performed Hauser-Feshbach calculations of the statistical component of the gamma emission, which dominates below approximately 15--16 MeV. The extended DSD model reproduces the spectral shapes and analyzing powers above this energy quite well. There is no evidence in the present reaction that additional mechanisms, such as multistep compound or multistep direct emission, are required

  14. Scattering effects of small-scale density fluctuations on reflectometric measurements in a tokamak plasma

    International Nuclear Information System (INIS)

    Garcia, J.P.; Manso, M.E.; Serra, F.M.; Mendonca, J.T.

    1989-01-01

    When a wave propagates in a non homogeneous fluctuating plasma part of the incident energy is scattered out to the nonlinear interaction between the wave and the oscillating modes perturbing the plasma. The possibility of enhanced scattering at the cutoff layer, where reflection of the incident wave occurs, has been recently suggested as the basis of a reflectometric experiment to determine the spatial location of small scale fluctuations in a fusion plasma. Here we report on the development of a theoretical model to evaluate the flux of energy scattered by fluctuations, in order to give insight about the interpretation of measurements using a microwave reflectometry diagnostic in a tokamak. The scattered field is obtained through the resolution of a (non-homogeneous) wave propagation equation where the source term is related with the nonlinear current due to the interaction between the incident wave and local fluctuations. We use a slab model for the plasma, and an ordinary (0) wave propagation along the density gradient is considered. The amplitude of the scattered wave at the border of the plasma is estimated. In order to know the contributions to the energy scattered both from the propagation region and the reflecting layer, an approach was used where perturbations are modelled by spatial step functions at several layers. The main contribution to the scattered power comes from the cutoff region, where the electric field amplitude swells as compared with the incident value. Considering the reflectometric system recently installed on the ASDEX tokamak, and using typical density profiles, expected values of the 'swelling factor' have been numerically evaluated. The role of incoherent scattering due to drift wave activity is discussed as well as the coherent scattering due to fluctuations induced by lower hybrid (LH) waves. (author) 2 refs., 4 figs

  15. Fluctuations in Overlapping Generations Economies

    DEFF Research Database (Denmark)

    Tvede, Mich

    . The approach to existence of endogenous fluctuations is basic in the sense that the prime ingredients are the implicit function theorem and linear algebra. Moreover the approach is applied to show that for an open and dense set of utility functions there exist endowment vectors such that sunspot equilibria...

  16. Magnetic fluctuations in turbulent flow

    International Nuclear Information System (INIS)

    Ruzmaikin, A.A.

    1990-01-01

    For dynamo excitation of the magnetic fluctuations in infinite fluid only a sufficient large magnetic Reynolds number is needed. In a infinite region an additional condition appears. Due to the diffusion of the magnetic field through the boundaries a size of the region must be large enough compare with a correlation length of the turbulence. Author)

  17. Firm default and aggregate fluctuations

    NARCIS (Netherlands)

    Jacobson, Tor; Linde, Jesper; Roszbach, Kasper

    This paper studies the relationship between macroeconomic fluctuations and corporate defaults while conditioning on industry affiliation and an extensive set of firm-specific factors. By using a panel data set for virtually all incorporated Swedish businesses over 1990-2009, a period which includes

  18. Fluctuating hydrodynamics for ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Lazaridis, Konstantinos [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States); Wickham, Logan [Department of Computer Science, Washington State University, Richland, 99354 (United States); Voulgarakis, Nikolaos, E-mail: n.voulgarakis@wsu.edu [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States)

    2017-04-25

    We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau–Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids. - Highlights: • A new fluctuating hydrodynamics method for ionic liquids. • Description of ionic liquid morphology in bulk and near electrified surfaces. • Direct comparison with experimental measurements.

  19. IKNO, a user facility for coherent terahertz and UV synchrotron radiation

    International Nuclear Information System (INIS)

    Sannibale, Fernando; Marcelli, Augusto; Innocenzi, Plinio

    2008-01-01

    IKNO (Innovation and KNOwledge) is a proposal for a multi-user facility based on an electron storage ring optimized for the generation of coherent synchrotron radiation (CSR) in the terahertz frequency range, and of broadband incoherent synchrotron radiation (SR) ranging from the IR to the VUV. IKNO can be operated in an ultra-stable CSR mode with photon flux in the terahertz frequency region up to nine orders of magnitude higher than in existing 3rd generation light sources. Simultaneously to the CSR operation, broadband incoherent SR up to VUV frequencies is available at the beamline ports. The main characteristics of the IKNO storage and its performance in terms of CSR and incoherent SR are described in this paper. The proposed location for the infrastructure facility is in Sardinia, Italy

  20. Black Hole Area Quantization rule from Black Hole Mass Fluctuations

    OpenAIRE

    Schiffer, Marcelo

    2016-01-01

    We calculate the black hole mass distribution function that follows from the random emission of quanta by Hawking radiation and with this function we calculate the black hole mass fluctuation. From a complete different perspective we regard the black hole as quantum mechanical system with a quantized event horizon area and transition probabilities among the various energy levels and then calculate the mass dispersion. It turns out that there is a perfect agreement between the statistical and ...

  1. The reduction of low frequency fluctuations in RFP experiments

    International Nuclear Information System (INIS)

    Phillips, J.A.; Baker, D.A.; Gribble, R.F.

    1998-01-01

    The low frequency fluctuations seen in RFP experiments are found to be correlated with changes in the toroidal flux measured by diamagnetic loops surrounding the discharge. The correlation of the onset of impurity radiation and x-rays with the crash seen in experiments is caused by plasma bombarding the metal liner associated with this loss of flux. Efforts should be made to design improved stabilizing shells that will reduce the loss of flux and give improved RFP energy confinement times

  2. Some fundamental considerations of the equation of radiative transfer

    International Nuclear Information System (INIS)

    Kuriyan, J.G.; Sudarshan, E.C.G.

    1978-10-01

    The radiation transfer of the vector electromagnetic field was first formulated by Chandrasekhar while deriving the polarization characteristics of a sunlit sky. There are two subtle problems underlying this treatment. The first concerns the crucial identification of a Stokes parameter with the specific intensity of radiation. While both depend on position in 3-D space, the latter has, intrinsic to it, an additional angular dependence defining the flow of the radiation field. How can this inadequacy be remedied without damaging the results obtained heretofore from Chandrasekhar's formalism. The second problem arises from the fact that the radiative transfer equation describes the transport of an incoherent radiation field through space. This, however, seems to contradict the results of the Van Cittert-Zernike-Wolf theorem which implies that an incoherent field develops coherence as it passes through free space implying, of course, that the radiative transfer equation must involve not incoherent but partially coherent fields. The vector transfer equation of the direct beam (Beer's law) is derived from first principles. The analysis of this equation provides a satisfactory resolution of these two problems. The result also shows that the Beer's law will have to be modified to a matrix law to accommodate systems that are not spherically symmetric. 13 references

  3. Coherent Forward Stimulated-Brillouin Scattering of a Spatially Incoherent Laser Beam in a Plasma and Its Effect on Beam Spray

    International Nuclear Information System (INIS)

    Grech, M.; Riazuelo, G.; Pesme, D.; Weber, S.; Tikhonchuk, V. T.

    2009-01-01

    A statistical model for forward stimulated-Brillouin scattering is developed for a spatially incoherent, monochromatic, laser beam propagating in a plasma. The threshold above which the laser beam spatial incoherence cannot prevent the coherent growth of forward stimulated-Brillouin scattering is computed. It is found to be well below the threshold for self-focusing. Three-dimensional simulations confirm its existence and reveal the onset of beam spray above it. From these results, we propose a new figure of merit for the control of propagation through a plasma of a spatially incoherent laser beam

  4. Analysis for probability of irradiance fluctuation; Nissha hendo kakuritsu no bunseki

    Energy Technology Data Exchange (ETDEWEB)

    Minowa, J; Kurokawa, K [Tokyo University of Agriculture and Technology, Tokyo (Japan); Otani, K; Sakuta, K [Electrochemical Laboratory, Tsukuba (Japan)

    1996-10-27

    Distribution of probabilities of solar radiation fluctuation was examined to learn the fluctuation in photovoltaic power generation efficiency for the purpose of improving on the generation system. The measuring setup comprised one base station and nine terminal stations. The terminal stations were arrayed in lattice so that a 4km{times}4km-large area would be covered. The standard deviation in solar radiation fluctuation at an observation spot ANNE stayed constant at approximately 0.1kW/m{sup 2} at all observation hours. In the vicinity of a clearness index range of 0.5-0.6 (a higher index showing a clearer weather) in the daytime, the index fluctuated very much, predicting a half-clear sky with scattered cloud. In the range of 0.2-0.3, fluctuation was small. In the range of 0.6-0.7, fluctuation was small and solar radiation was stable under the clear sky. The scope of fluctuation in the areal average is smaller than that in the average at each of the terminal stations, which is explained by the even-out effect. This means that, if multiple PV systems concentratedly introduced into one region are appropriately coordinated, the outputs from the individual PV systems that are naturally inconsistent are evened out and that the reliability of the network as a whole is consequently enhanced. 5 refs., 7 figs., 1 tab.

  5. Pressure dependence of coherence-incoherence crossover behavior in KFe2As2 observed by resistivity and 75As-NMR/NQR

    Science.gov (United States)

    Wiecki, P.; Taufour, V.; Chung, D. Y.; Kanatzidis, M. G.; Bud'ko, S. L.; Canfield, P. C.; Furukawa, Y.

    2018-02-01

    We present the results of 75As nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and resistivity measurements in KFe2As2 under pressure (p ). The temperature dependence of the NMR shift, nuclear spin-lattice relaxation time (T1), and resistivity show a crossover between a high-temperature incoherent, local-moment behavior and a low-temperature coherent behavior at a crossover temperature (T*). T* is found to increase monotonically with pressure, consistent with increasing hybridization between localized 3 d orbital-derived bands with the itinerant electron bands. No anomaly in T* is seen at the critical pressure pc=1.8 GPa where a change of slope of the superconducting (SC) transition temperature Tc(p ) has been observed. In contrast, Tc(p ) seems to correlate with antiferromagnetic spin fluctuations in the normal state as measured by the NQR 1 /T1 data, although such a correlation cannot be seen in the replacement effects of A in the A Fe2As2 (A =K , Rb, Cs) family. In the superconducting state, two T1 components are observed at low temperatures, suggesting the existence of two distinct local electronic environments. The temperature dependence of the short T1 s indicates a nearly gapless state below Tc. On the other hand, the temperature dependence of the long component 1 /T1 L implies a large reduction in the density of states at the Fermi level due to the SC gap formation. These results suggest a real-space modulation of the local SC gap structure in KFe2As2 under pressure.

  6. Fluctuation current in superconducting loops

    International Nuclear Information System (INIS)

    Berger, Jorge

    2012-01-01

    A superconducting loop that encloses noninteger flux holds a permanent current. On the average, this current is also present above T c , and has been measured in recent years. We are able to evaluate the permanent current within the TDGL or the Kramer-Watts-Tobin models for loops of general configuration, i.e., we don't require uniform cross section, material or temperature. We can also consider situations in which the width is not negligible in comparison to the radius. Our results agree with experiments. The situations with which we deal at present include fluctuation superconductivity in two-band superconductors, equilibrium thermal fluctuations of supercurrent along a weak link, and ratchet effects.

  7. Fluctuations and confinement in ATF

    International Nuclear Information System (INIS)

    Isler, R.C.; Harris, J.H.; Murakami, M.

    1993-01-01

    In the period immediately prior to the suspension of ATF operation in November, 1991, a great deal of emphasis was palced on investigations of the fundamental mechanisms controlling confinement in this device. At that time, measurements of the density fluctuations throughout the plasma volume indicated the existence of theoretically predicted dissipative trapped electron and resistive interchange instabilities. These identifications were supported by results of dynamic configuration scans of the magnetic fields during which the extent of the magnetic well, shear, and fraction of confined trapped particles were changed continuously. Interpretation of the data from these experiments has been an ongoing exercise. Most recently, analysis of discharges employing strong gas puffing to change density gradients and fluctuation levels have strengthened the view that dissipative trapped electron modes may be present but do not play a significant direct role in energy transport. The present paper summarizes the current understanding concerning the identification of instabilities and their relationship to confinement in ATF

  8. Charge Fluctuations in Nanoscale Capacitors

    Science.gov (United States)

    Limmer, David T.; Merlet, Céline; Salanne, Mathieu; Chandler, David; Madden, Paul A.; van Roij, René; Rotenberg, Benjamin

    2013-09-01

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with histogram reweighting techniques. This approach offers, in particular, an efficient, accurate, and physically insightful route to the differential capacitance that is broadly applicable. We demonstrate these methods with three different capacitors: pure water between platinum electrodes and a pure as well as a solvent-based organic electrolyte each between graphite electrodes. The total charge distributions with the pure solvent and solvent-based electrolytes are remarkably Gaussian, while in the pure ionic liquid the total charge distribution displays distinct non-Gaussian features, suggesting significant potential-driven changes in the organization of the interfacial fluid.

  9. Charge fluctuations in nanoscale capacitors.

    Science.gov (United States)

    Limmer, David T; Merlet, Céline; Salanne, Mathieu; Chandler, David; Madden, Paul A; van Roij, René; Rotenberg, Benjamin

    2013-09-06

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with histogram reweighting techniques. This approach offers, in particular, an efficient, accurate, and physically insightful route to the differential capacitance that is broadly applicable. We demonstrate these methods with three different capacitors: pure water between platinum electrodes and a pure as well as a solvent-based organic electrolyte each between graphite electrodes. The total charge distributions with the pure solvent and solvent-based electrolytes are remarkably Gaussian, while in the pure ionic liquid the total charge distribution displays distinct non-Gaussian features, suggesting significant potential-driven changes in the organization of the interfacial fluid.

  10. Fluctuation theorems and atypical trajectories

    International Nuclear Information System (INIS)

    Sahoo, M; Lahiri, S; Jayannavar, A M

    2011-01-01

    In this work, we have studied simple models that can be solved analytically to illustrate various fluctuation theorems. These fluctuation theorems provide symmetries individually to the distributions of physical quantities such as the classical work (W c ), thermodynamic work (W), total entropy (Δs tot ) and dissipated heat (Q), when the system is driven arbitrarily out of equilibrium. All these quantities can be defined for individual trajectories. We have studied the number of trajectories which exhibit behaviour unexpected at the macroscopic level. As the time of observation increases, the fraction of such atypical trajectories decreases, as expected at the macroscale. The distributions for the thermodynamic work and entropy production in nonlinear models may exhibit a peak (most probable value) in the atypical regime without violating the expected average behaviour. However, dissipated heat and classical work exhibit a peak in the regime of typical behaviour only.

  11. Random numbers from vacuum fluctuations

    International Nuclear Information System (INIS)

    Shi, Yicheng; Kurtsiefer, Christian; Chng, Brenda

    2016-01-01

    We implement a quantum random number generator based on a balanced homodyne measurement of vacuum fluctuations of the electromagnetic field. The digitized signal is directly processed with a fast randomness extraction scheme based on a linear feedback shift register. The random bit stream is continuously read in a computer at a rate of about 480 Mbit/s and passes an extended test suite for random numbers.

  12. Random numbers from vacuum fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yicheng; Kurtsiefer, Christian, E-mail: christian.kurtsiefer@gmail.com [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Center for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Chng, Brenda [Center for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore)

    2016-07-25

    We implement a quantum random number generator based on a balanced homodyne measurement of vacuum fluctuations of the electromagnetic field. The digitized signal is directly processed with a fast randomness extraction scheme based on a linear feedback shift register. The random bit stream is continuously read in a computer at a rate of about 480 Mbit/s and passes an extended test suite for random numbers.

  13. The Applicability of Incoherent Array Processing to IMS Seismic Array Stations

    Science.gov (United States)

    Gibbons, S. J.

    2012-04-01

    The seismic arrays of the International Monitoring System for the CTBT differ greatly in size and geometry, with apertures ranging from below 1 km to over 60 km. Large and medium aperture arrays with large inter-site spacings complicate the detection and estimation of high frequency phases since signals are often incoherent between sensors. Many such phases, typically from events at regional distances, remain undetected since pipeline algorithms often consider only frequencies low enough to allow coherent array processing. High frequency phases that are detected are frequently attributed qualitatively incorrect backazimuth and slowness estimates and are consequently not associated with the correct event hypotheses. This can lead to missed events both due to a lack of contributing phase detections and by corruption of event hypotheses by spurious detections. Continuous spectral estimation can be used for phase detection and parameter estimation on the largest aperture arrays, with phase arrivals identified as local maxima on beams of transformed spectrograms. The estimation procedure in effect measures group velocity rather than phase velocity and the ability to estimate backazimuth and slowness requires that the spatial extent of the array is large enough to resolve time-delays between envelopes with a period of approximately 4 or 5 seconds. The NOA, AKASG, YKA, WRA, and KURK arrays have apertures in excess of 20 km and spectrogram beamforming on these stations provides high quality slowness estimates for regional phases without additional post-processing. Seven arrays with aperture between 10 and 20 km (MJAR, ESDC, ILAR, KSRS, CMAR, ASAR, and EKA) can provide robust parameter estimates subject to a smoothing of the resulting slowness grids, most effectively achieved by convolving the measured slowness grids with the array response function for a 4 or 5 second period signal. The MJAR array in Japan recorded high SNR Pn signals for both the 2006 and 2009 North Korea

  14. Subtype differentiation of renal tumors using voxel-based histogram analysis of intravoxel incoherent motion parameters.

    Science.gov (United States)

    Gaing, Byron; Sigmund, Eric E; Huang, William C; Babb, James S; Parikh, Nainesh S; Stoffel, David; Chandarana, Hersh

    2015-03-01

    The aim of this study was to determine if voxel-based histogram analysis of intravoxel incoherent motion imaging (IVIM) parameters can differentiate various subtypes of renal tumors, including benign and malignant lesions. A total of 44 patients with renal tumors who underwent surgery and had histopathology available were included in this Health Insurance Portability and Accountability Act-compliant, institutional review board-approved, single-institution prospective study. In addition to routine renal magnetic resonance imaging examination performed on a 1.5-T system, all patients were imaged with axial diffusion-weighted imaging using 8 b values (range, 0-800 s/mm). A biexponential model was fitted to the diffusion signal data using a segmented algorithm to extract the IVIM parameters perfusion fraction (fp), tissue diffusivity (Dt), and pseudodiffusivity (Dp) for each voxel. Mean and histogram measures of heterogeneity (standard deviation, skewness, and kurtosis) of IVIM parameters were correlated with pathology results of tumor subtype using unequal variance t tests to compare subtypes in terms of each measure. Correction for multiple comparisons was accomplished using the Tukey honestly significant difference procedure. A total of 44 renal tumors including 23 clear cell (ccRCC), 4 papillary (pRCC), 5 chromophobe, and 5 cystic renal cell carcinomas, as well as benign lesions, 4 oncocytomas (Onc) and 3 angiomyolipomas (AMLs), were included in our analysis. Mean IVIM parameters fp and Dt differentiated 8 of 15 pairs of renal tumors. Histogram analysis of IVIM parameters differentiated 9 of 15 subtype pairs. One subtype pair (ccRCC vs pRCC) was differentiated by mean analysis but not by histogram analysis. However, 2 other subtype pairs (AML vs Onc and ccRCC vs Onc) were differentiated by histogram distribution parameters exclusively. The standard deviation of Dt [σ(Dt)] differentiated ccRCC (0.362 ± 0.136 × 10 mm/s) from AML (0.199 ± 0.043 × 10 mm/s) (P = 0

  15. Quantum Fluctuations for Gravitational Impulsive Waves

    OpenAIRE

    Enginer, Y.; Hortacsu, M.; Ozdemir, N.

    1998-01-01

    Quantum fluctuations for a massless scalar field in the background metric of spherical impulsive gravitational waves through Minkowski and de Sitter spaces are investigated. It is shown that there exist finite fluctuations for de Sitter space.

  16. Net charge fluctuations and local charge compensation

    International Nuclear Information System (INIS)

    Fu Jinghua

    2006-01-01

    We propose net charge fluctuation as a measure of local charge correlation length. It is demonstrated that, in terms of a schematic multiperipheral model, net charge fluctuation satisfies the same Quigg-Thomas relation as satisfied by charge transfer fluctuation. Net charge fluctuations measured in finite rapidity windows depend on both the local charge correlation length and the size of the observation window. When the observation window is larger than the local charge correlation length, the net charge fluctuation only depends on the local charge correlation length, while forward-backward charge fluctuations always have strong dependence on the observation window size. Net charge fluctuations and forward-backward charge fluctuations measured in the present heavy ion experiments show characteristic features similar to those from multiperipheral models. But the data cannot all be understood within this simple model

  17. Measurement of magnetic fluctuation induced energy transport

    International Nuclear Information System (INIS)

    Fiksel, G.; Prager, S.C.; Shen, W.; Stoneking, M.

    1993-11-01

    The local electron energy flux produced by magnetic fluctuations has been measured directly in the MST reversed field pinch (over the radial range r/a > 0.75). The flux, produced by electrons traveling parallel to a fluctuating magnetic field, is obtained from correlation between the fluctuations in the parallel heat flux and the radial magnetic field. The fluctuation induced flux is large (100 kW/cm 2 ) in the ''core'' (r/a 2 ) in the edge

  18. Pressure Fluctuations Induced by a Hypersonic Turbulent Boundary Layer

    Science.gov (United States)

    Duan, Lian; Choudhari, Meelan M.; Zhang, Chao

    2016-01-01

    Direct numerical simulations (DNS) are used to examine the pressure fluctuations generated by a spatially-developed Mach 5.86 turbulent boundary layer. The unsteady pressure field is analyzed at multiple wall-normal locations, including those at the wall, within the boundary layer (including inner layer, the log layer, and the outer layer), and in the free stream. The statistical and structural variations of pressure fluctuations as a function of wall-normal distance are highlighted. Computational predictions for mean velocity pro les and surface pressure spectrum are in good agreement with experimental measurements, providing a first ever comparison of this type at hypersonic Mach numbers. The simulation shows that the dominant frequency of boundary-layer-induced pressure fluctuations shifts to lower frequencies as the location of interest moves away from the wall. The pressure wave propagates with a speed nearly equal to the local mean velocity within the boundary layer (except in the immediate vicinity of the wall) while the propagation speed deviates from the Taylor's hypothesis in the free stream. Compared with the surface pressure fluctuations, which are primarily vortical, the acoustic pressure fluctuations in the free stream exhibit a significantly lower dominant frequency, a greater spatial extent, and a smaller bulk propagation speed. The freestream pressure structures are found to have similar Lagrangian time and spatial scales as the acoustic sources near the wall. As the Mach number increases, the freestream acoustic fluctuations exhibit increased radiation intensity, enhanced energy content at high frequencies, shallower orientation of wave fronts with respect to the flow direction, and larger propagation velocity.

  19. A design of a wavelength-hopping time-spreading incoherent optical code division multiple access system

    International Nuclear Information System (INIS)

    Glesk, I.; Baby, V.

    2005-01-01

    We present the architecture and code design for a highly scalable, 2.5 Gb/s per user optical code division multiple access (OCDMA) system. The system is scalable to 100 potential and more than 10 simultaneous users, each with a bit error rate (BER) of less than 10 -9 . The system architecture uses a fast wavelength-hopping, time-spreading codes. Unlike frequency and phase sensitive coherent OCDMA systems, this architecture utilizes standard on off keyed optical pulses allocated in the time and wavelength dimensions. This incoherent OCDMA approach is compatible with existing WDM optical networks and utilizes off the shelf components. We discuss the novel optical subsystem design for encoders and decoders that enable the realization of a highly scalable incoherent OCDMA system with rapid reconfigurability. A detailed analysis of the scalability of the two dimensional code is presented and select network deployment architectures for OCDMA are discussed (Authors)

  20. Intravoxel Incoherent Motion in Normal Pituitary Gland: Initial Study with Turbo Spin-Echo Diffusion-Weighted Imaging.

    Science.gov (United States)

    Kamimura, K; Nakajo, M; Fukukura, Y; Iwanaga, T; Saito, T; Sasaki, M; Fujisaki, T; Takemura, A; Okuaki, T; Yoshiura, T

    2016-12-01

    DWI with conventional single-shot EPI of the pituitary gland is hampered by strong susceptibility artifacts. Our purpose was to evaluate the feasibility of intravoxel incoherent motion assessment by using DWI based on TSE of the normal anterior pituitary lobe. The intravoxel incoherent motion parameters, including the true diffusion coefficient (D), the perfusion fraction (f), and the pseudo-diffusion coefficient (D*), were obtained with TSE-DWI in 5 brain regions (the pons, the WM and GM of the vermis, and the genu and splenium of the corpus callosum) in 8 healthy volunteers, and their agreement with those obtained with EPI-DWI was evaluated by using the intraclass correlation coefficient. The 3 intravoxel incoherent motion parameters in the anterior pituitary lobe were compared with those in the brain regions by using the Dunnett test. The agreement between TSE-DWI and EPI-DWI was moderate (intraclass correlation coefficient = 0.571) for D, substantial (0.699) for f', but fair (0.405) for D*. D in the anterior pituitary lobe was significantly higher than in the 5 brain regions (P anterior pituitary lobe was significantly higher than in the 5 brain regions (P pituitary D* was not significantly different from that in the 5 brain regions. Our results demonstrated the feasibility of intravoxel incoherent motion assessment of the normal anterior pituitary lobe by using TSE-DWI. High D and f values in the anterior pituitary lobe were thought to reflect its microstructural and perfusion characteristics. © 2016 by American Journal of Neuroradiology.

  1. Current-induced magnetization changes in a spin valve due to incoherent emission of non-equilibrium magnons

    OpenAIRE

    Kozub, V. I.; Caro, J.

    2004-01-01

    We describe spin transfer in a ferromagnet/normal metal/ferromagnet spin-valve point contact. Spin is transferred from the spin-polarized device current to the magnetization of the free layer by the mechanism of incoherent magnon emission by electrons. Our approach is based on the rate equation for the magnon occupation, using Fermi's golden rule for magnon emission and absorption and the non-equilibrium electron distribution for a biased spin valve. The magnon emission reduces the magnetizat...

  2. Electron temperature measurements by the plasma line technique at the French incoherent scatter radar facilities

    International Nuclear Information System (INIS)

    Kofman, W.; Lejeune, G.; Hagfors, T.; Bauer, P.

    1981-01-01

    The results of experiments aimed at the determination of the electron temperature by a plasma line technique are presented. Using the multistatic capabilities of the French incoherent scatter radar, the plasma line frequencies were simultaneously measured at two receiving stations (Mende and Nancay) at the altitude corresponding to the maximum of the F layer. Different plasma line frequencies are measued because of different effective k vectors that appear in the thermal term of the plasma dispersion relation. We derive and apply two data analysis procedures that enable us to determine this frequency difference. Comparison of this measured frequency difference to that calculated using the ion component electron temperature demonstrates that the plasma lines could indeed be used to determine the electron temperature. A strong dependence of the power in the plasma line as a function of the angle between k vector and magnetic field is observed in agreement with the theory. The future developments of this technique with the EISCAT radar facilities are discussed

  3. Chronic kidney disease: Pathological and functional evaluation with intravoxel incoherent motion diffusion-weighted imaging.

    Science.gov (United States)

    Mao, Wei; Zhou, Jianjun; Zeng, Mengsu; Ding, Yuqin; Qu, Lijie; Chen, Caizhong; Ding, Xiaoqiang; Wang, Yaqiong; Fu, Caixia

    2018-05-01

    Because chronic kidney disease (CKD) is a worldwide problem, accurate pathological and functional evaluation is required for planning treatment and follow-up. Intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) can assess both capillary perfusion and tissue diffusion and may be helpful in evaluating renal function and pathology. To evaluate functional and pathological alterations in CKD by applying IVIM-DWI. Prospective study. In all, 72 CKD patients who required renal biopsy and 20 healthy volunteers. 1.5T. All subjects underwent IVIM-DWI of the kidneys, and image analysis was performed by two radiologists. The mean values of true diffusion coefficient (D), pseudo diffusion coefficient (D*), and perfusion fraction (f) were acquired from renal parenchyma. Correlation between IVIM-DWI parameters and estimated glomerular filtration rate (eGFR), as well as pathological damage, were assessed. One-way analysis of variance (ANOVA), paired sample t-test and Spearman correlation analysis. The paired sample t-test revealed that IVIM-DWI parameters were significantly lower in medulla than cortex for both patients and controls (P Imaging 2018;47:1251-1259. © 2017 International Society for Magnetic Resonance in Medicine.

  4. An efficient central DOA tracking algorithm for multiple incoherently distributed sources

    Science.gov (United States)

    Hassen, Sonia Ben; Samet, Abdelaziz

    2015-12-01

    In this paper, we develop a new tracking method for the direction of arrival (DOA) parameters assuming multiple incoherently distributed (ID) sources. The new approach is based on a simple covariance fitting optimization technique exploiting the central and noncentral moments of the source angular power densities to estimate the central DOAs. The current estimates are treated as measurements provided to the Kalman filter that model the dynamic property of directional changes for the moving sources. Then, the covariance-fitting-based algorithm and the Kalman filtering theory are combined to formulate an adaptive tracking algorithm. Our algorithm is compared to the fast approximated power iteration-total least square-estimation of signal parameters via rotational invariance technique (FAPI-TLS-ESPRIT) algorithm using the TLS-ESPRIT method and the subspace updating via FAPI-algorithm. It will be shown that the proposed algorithm offers an excellent DOA tracking performance and outperforms the FAPI-TLS-ESPRIT method especially at low signal-to-noise ratio (SNR) values. Moreover, the performances of the two methods increase as the SNR values increase. This increase is more prominent with the FAPI-TLS-ESPRIT method. However, their performances degrade when the number of sources increases. It will be also proved that our method depends on the form of the angular distribution function when tracking the central DOAs. Finally, it will be shown that the more the sources are spaced, the more the proposed method can exactly track the DOAs.

  5. Intravoxel incoherent motion magnetic resonance imaging to predict vesicoureteral reflux in children with urinary tract infection

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Woo; Lee, Chang Hee; Park, Yang Shin; Kim, Kyeong Ah; Park, Cheol Min [Korea University College of Medicine, Departments of Radiology, Korea University Guro Hospital, 80 Guro-dong, Guro-gu, Seoul (Korea, Republic of); Yoo, Kee Hwan [Korea University College of Medicine, Departments of Pediatrics, Korea University Guro Hospital, Seoul (Korea, Republic of); Je, Bo-Kyung [Korea University College of Medicine, Department of Radiology, Korea University Ansan Hospital, Seoul (Korea, Republic of); Kiefer, Berthold [Oncology Application Development, Siemens Healthcare, Erlangen (Germany)

    2016-06-15

    To compare the diffusion parameters of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) between the ''reflux'' and the ''non-reflux'' kidneys, and to evaluate the feasibility of using IVIM DWI to predict vesicoureteral reflux (VUR) in children with a urinary tract infection (UTI). Eighty-three kidneys from 57 pediatric patients with a UTI were classified into ''reflux'' and ''non-reflux'' groups according to voiding cystourethrography (VCUG) results. The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (PF) were measured and compared in the renal pelvis of both groups. Four indices (D*/ADC, PF/ADC, D*/D, and PF/D) were calculated and receiver operating characteristic (ROC) curve analyses were performed. VURs were detected on VCUG in 21 kidneys. PF and D* were significantly higher in the ''reflux'' group than in the ''non-reflux'' group. The indices were all significantly higher. The PF/D index showed the best diagnostic performance in predicting VUR in children with UTI (A{sub z} = 0.864). PF and D* were significantly higher in the ''reflux'' kidney than in the ''non-reflux'' kidney. Our new index (PF/D) could prove useful for predicting VUR. (orig.)

  6. Intravoxel incoherent motion perfusion imaging in acute stroke: initial clinical experience

    International Nuclear Information System (INIS)

    Federau, C.; Becce, F.; Maeder, P.; Meuli, R.; Sumer, S.; Wintermark, M.; O'Brien, K.

    2014-01-01

    Intravoxel incoherent motion (IVIM) imaging is an MRI perfusion technique that uses a diffusion-weighted sequence with multiple b values and a bi-compartmental signal model to measure the so-called pseudo-diffusion of blood caused by its passage through the microvascular network. The goal of the current study was to assess the feasibility of IVIM perfusion fraction imaging in patients with acute stroke. Images were collected in 17 patients with acute stroke. Exclusion criteria were onset of symptoms to imaging >5 days, hemorrhagic transformation, infratentorial lesions, small lesions 2 . Image quality was assessed by two radiologists, and quantitative analysis was performed in regions of interest placed in the stroke area, defined by thresholding the apparent diffusion coefficient maps, as well as in the contralateral region. IVIM perfusion fraction maps showed an area of decreased perfusion fraction f in the region of decreased apparent diffusion coefficient. Quantitative analysis showed a statistically significant decrease in both IVIM perfusion fraction f (0.026 ± 0.019 vs. 0.056 ± 0.025, p = 2.2 . 10 -6 ) and diffusion coefficient D compared with the contralateral side (3.9 ± 0.79 . 10 -4 vs. 7.5 ± 0.86 . 10 -4 mm 2 /s, p = 1.3 . 10 -20 ). IVIM perfusion fraction imaging is feasible in acute stroke. IVIM perfusion fraction is significantly reduced in the visible infarct. Further studies should evaluate the potential for IVIM to predict clinical outcome and treatment response. (orig.)

  7. Combined distributed Raman and Bragg fiber temperature sensing using incoherent optical frequency domain reflectometry

    Directory of Open Access Journals (Sweden)

    M. Koeppel

    2018-02-01

    Full Text Available Optical temperature sensors offer unique features which make them indispensable for key industries such as the energy sector. However, commercially available systems are usually designed to perform either distributed or distinct hot spot temperature measurements since they are restricted to one measurement principle. We have combined two concepts, fiber Bragg grating (FBG temperature sensors and Raman-based distributed temperature sensing (DTS, to overcome these limitations. Using a technique called incoherent optical frequency domain reflectometry (IOFDR, it is possible to cascade several FBGs with the same Bragg wavelength in one fiber and simultaneously perform truly distributed Raman temperature measurements. In our lab we have achieved a standard deviation of 2.5 K or better at a spatial resolution in the order of 1 m with the Raman DTS. We have also carried out a field test in a high-voltage environment with strong magnetic fields where we performed simultaneous Raman and FBG temperature measurements using a single sensor fiber only.

  8. Intravoxel Incoherent Motion Diffusion-weighted Imaging: Evaluation of the Differentiation of Solid Hepatic Lesions

    Directory of Open Access Journals (Sweden)

    Ma Luo

    2017-10-01

    Full Text Available PURPOSE: To evaluate whether intravoxel incoherent motion (IVIM–related parameters could be used to differentiate malignant from benign focal liver lesions (FLLs and to improve diagnostic efficiency. METHODS: Seventy-four patients with 75 lesions, including 51 malignant FLLs and 24 benign FLLs, underwent liver 3.0-T magnetic resonance imaging for routine examination sequences. IVIM diffusion-weighted imaging (DWI with 11 b values (0-800 s/mm2 was also acquired concurrently. Apparent diffusion coefficient (ADCtotal and IVIM-derived parameters, such as the pure diffusion coefficient (D, the pseudodiffusion coefficient (D⁎, and the perfusion fraction (f, were calculated and compared between the two groups. A receiver operating characteristic curve analysis was performed to assess their diagnostic value. RESULTS: ADCtotal, D, and f were significantly lower in the malignant group than in the benign group, whereas D⁎ did not show a statistical difference. D had a larger area under the curve value (0.968 and higher sensitivity (92.30% for differentiation. CONCLUSION: IVIM is a useful method to differentiate malignant and benign FLLs. The D value showed higher efficacy to detect hepatic solid lesions.

  9. All-fiber 7x1 signal combiner for incoherent laser beam combining

    Science.gov (United States)

    Noordegraaf, D.; Maack, M. D.; Skovgaard, P. M. W.; Johansen, J.; Becker, F.; Belke, S.; Blomqvist, M.; Laegsgaard, J.

    2011-02-01

    We demonstrate an all-fiber 7x1 signal combiner for incoherent laser beam combining. This is a potential key component for reaching several kW of stabile laser output power. The combiner couples the output from 7 single-mode (SM) fiber lasers into a single multi-mode (MM) fiber. The input signal fibers have a core diameter of 17 μm and the output MM fiber has a core diameter of 100 μm. In a tapered section light gradually leaks out of the SM fibers and is captured by a surrounding fluorine-doped cladding. The combiner is tested up to 2.5 kW of combined output power and only a minor increase in device temperature is observed. At an intermediate power level of 600 W a beam parameter product (BPP) of 2.22 mm x mrad is measured, corresponding to an M2 value of 6.5. These values are approaching the theoretical limit dictated by brightness conservation.

  10. Comparison of the UAF Ionosphere Model with Incoherent-Scatter Radar Data

    Science.gov (United States)

    McAllister, J.; Maurits, S.; Kulchitsky, A.; Watkins, B.

    2004-12-01

    The UAF Eulerian Parallel Polar Ionosphere Model (UAF EPPIM) is a first-principles three-dimensional time-dependent representation of the northern polar ionosphere (>50 degrees north latitude). The model routinely generates short-term (~2 hours) ionospheric forecasts in real-time. It may also be run in post-processing/batch mode for specific time periods, including long-term (multi-year) simulations. The model code has been extensively validated (~100k comparisons/model year) against ionosonde foF2 data during quiet and moderate solar activity in 2002-2004 with reasonable fidelity (typical relative RMS 10-20% for summer daytime, 30-50% winter nighttime). However, ionosonde data is frequently not available during geomagnetic disturbances. The objective of the work reported here is to compare model outputs with available incoherent-scatter radar data during the storm period of October-November 2003. Model accuracy is examined for this period and compared to model performance during geomagnetically quiet and moderate circumstances. Possible improvements are suggested which are likely to boost model fidelity during storm conditions.

  11. Sparse synthetic aperture with Fresnel elements (S-SAFE) using digital incoherent holograms

    Science.gov (United States)

    Kashter, Yuval; Rivenson, Yair; Stern, Adrian; Rosen, Joseph

    2015-01-01

    Creating a large-scale synthetic aperture makes it possible to break the resolution boundaries dictated by the wave nature of light of common optical systems. However, their implementation is challenging, since the generation of a large size continuous mosaic synthetic aperture composed of many patterns is complicated in terms of both phase matching and time-multiplexing duration. In this study we present an advanced configuration for an incoherent holographic imaging system with super resolution qualities that creates a partial synthetic aperture. The new system, termed sparse synthetic aperture with Fresnel elements (S-SAFE), enables significantly decreasing the number of the recorded elements, and it is free from positional constrains on their location. Additionally, in order to obtain the best image quality we propose an optimal mosaicking structure derived on the basis of physical and numerical considerations, and introduce three reconstruction approaches which are compared and discussed. The super-resolution capabilities of the proposed scheme and its limitations are analyzed, numerically simulated and experimentally demonstrated. PMID:26367947

  12. Incoherent digital holograms acquired by interferenceless coded aperture correlation holography system without refractive lenses.

    Science.gov (United States)

    Kumar, Manoj; Vijayakumar, A; Rosen, Joseph

    2017-09-14

    We present a lensless, interferenceless incoherent digital holography technique based on the principle of coded aperture correlation holography. The acquired digital hologram by this technique contains a three-dimensional image of some observed scene. Light diffracted by a point object (pinhole) is modulated using a random-like coded phase mask (CPM) and the intensity pattern is recorded and composed as a point spread hologram (PSH). A library of PSHs is created using the same CPM by moving the pinhole to all possible axial locations. Intensity diffracted through the same CPM from an object placed within the axial limits of the PSH library is recorded by a digital camera. The recorded intensity this time is composed as the object hologram. The image of the object at any axial plane is reconstructed by cross-correlating the object hologram with the corresponding component of the PSH library. The reconstruction noise attached to the image is suppressed by various methods. The reconstruction results of multiplane and thick objects by this technique are compared with regular lens-based imaging.

  13. Global measures of ionospheric electrodynamic activity inferred from combined incoherent scatter radar and ground magnetometer observations

    International Nuclear Information System (INIS)

    Richmond, A.D.; Kamide, Y.; Akasofu, S.I.; Alcayde, D.; Blanc, M.; De LaBeaujardiere, O.; Evans, D.S.; Foster, J.C.; Holt, J.M.; Friis-Christensen, E.; Pellinen, R.J.; Senior, C.; Zaitzev, A.N.

    1990-01-01

    An analysis of several global measures of high-latitude ionospheric electrodynamic activity is undertakn on the basis of results obtained from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure applied to incoherent scatter radar and ground magnetometer observatons for January 18-19, 1984. Different global measures of electric potentials, currents, resistances, and energy transfer from the magnetosphere show temporal variations that are generally well correlated. The authors present parameterizations of thees quantities in terms of the AE index and the hemispheric power index of precipitating auroral particles. It is shown how error estimates of the mapped electric fields can be used to correct the estimation of Joule heating. Global measures of potential drop, field-aligned current, and Joule heating as obtained by the AMIE procedure are compared with similar measures presented in previous studies. Agreement is found to within the uncertainties inherent in each study. The mean potential drop through which field-aligned currents flow in closing through the ionosphere is approximately 28% of the total polar cap potential drop under all conditions during these 2 days. They note that order-of-magnitude differences can appear when comparing different global measures of total electric current flow and of effective resistances of the global circuit, so that care must be exercised in choosing characteristic values of these parameters for circuit-analogy studies of ionosphere-magnetosphere electrodynamic coupling

  14. Incoherent manipulation of the photoactive yellow protein photocycle with dispersed pump-dump-probe spectroscopy.

    Science.gov (United States)

    Larsen, Delmar S; van Stokkum, Ivo H M; Vengris, Mikas; van Der Horst, Michael A; de Weerd, Frank L; Hellingwerf, Klaas J; van Grondelle, Rienk

    2004-09-01

    Photoactive yellow protein is the protein responsible for initiating the "blue-light vision" of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast pump-dump-probe spectroscopy, where the photocycle can be started and interrupted with appropriately tuned and timed laser pulses. This "incoherent" manipulation of the photocycle allows for the detailed spectroscopic investigation of the underlying photocycle dynamics and the construction of a fully self-consistent dynamical model. This model requires three kinetically distinct excited-state intermediates, two (ground-state) photocycle intermediates, I(0) and pR, and a ground-state intermediate through which the protein, after unsuccessful attempts at initiating the photocycle, returns to the equilibrium ground state. Also observed is a previously unknown two-photon ionization channel that generates a radical and an ejected electron into the protein environment. This second excitation pathway evolves simultaneously with the pathway containing the one-photon photocycle intermediates.

  15. Noise processing by microRNA-mediated circuits: The Incoherent Feed-Forward Loop, revisited

    Directory of Open Access Journals (Sweden)

    Silvia Grigolon

    2016-04-01

    Full Text Available The intrinsic stochasticity of gene expression is usually mitigated in higher eukaryotes by post-transcriptional regulation channels that stabilise the output layer, most notably protein levels. The discovery of small non-coding RNAs (miRNAs in specific motifs of the genetic regulatory network has led to identifying noise buffering as the possible key function they exert in regulation. Recent in vitro and in silico studies have corroborated this hypothesis. It is however also known that miRNA-mediated noise reduction is hampered by transcriptional bursting in simple topologies. Here, using stochastic simulations validated by analytical calculations based on van Kampen's expansion, we revisit the noise-buffering capacity of the miRNA-mediated Incoherent Feed Forward Loop (IFFL, a small module that is widespread in the gene regulatory networks of higher eukaryotes, in order to account for the effects of intermittency in the transcriptional activity of the modulator gene. We show that bursting considerably alters the circuit's ability to control static protein noise. By comparing with other regulatory architectures, we find that direct transcriptional regulation significantly outperforms the IFFL in a broad range of kinetic parameters. This suggests that, under pulsatile inputs, static noise reduction may be less important than dynamical aspects of noise and information processing in characterising the performance of regulatory elements.

  16. Intravoxel incoherent motion magnetic resonance imaging to predict vesicoureteral reflux in children with urinary tract infection

    International Nuclear Information System (INIS)

    Kim, Jeong Woo; Lee, Chang Hee; Park, Yang Shin; Kim, Kyeong Ah; Park, Cheol Min; Yoo, Kee Hwan; Je, Bo-Kyung; Kiefer, Berthold

    2016-01-01

    To compare the diffusion parameters of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) between the ''reflux'' and the ''non-reflux'' kidneys, and to evaluate the feasibility of using IVIM DWI to predict vesicoureteral reflux (VUR) in children with a urinary tract infection (UTI). Eighty-three kidneys from 57 pediatric patients with a UTI were classified into ''reflux'' and ''non-reflux'' groups according to voiding cystourethrography (VCUG) results. The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (PF) were measured and compared in the renal pelvis of both groups. Four indices (D*/ADC, PF/ADC, D*/D, and PF/D) were calculated and receiver operating characteristic (ROC) curve analyses were performed. VURs were detected on VCUG in 21 kidneys. PF and D* were significantly higher in the ''reflux'' group than in the ''non-reflux'' group. The indices were all significantly higher. The PF/D index showed the best diagnostic performance in predicting VUR in children with UTI (A z = 0.864). PF and D* were significantly higher in the ''reflux'' kidney than in the ''non-reflux'' kidney. Our new index (PF/D) could prove useful for predicting VUR. (orig.)

  17. A new method for incoherent combining of far-field laser beams based on multiple faculae recognition

    Science.gov (United States)

    Ye, Demao; Li, Sichao; Yan, Zhihui; Zhang, Zenan; Liu, Yuan

    2018-03-01

    Compared to coherent beam combining, incoherent beam combining can complete the output of high power laser beam with high efficiency, simple structure, low cost and high thermal damage resistance, and it is easy to realize in engineering. Higher target power is achieved by incoherent beam combination which using technology of multi-channel optical path correction. However, each channel forms a spot in the far field respectively, which cannot form higher laser power density with low overlap ratio of faculae. In order to improve the combat effectiveness of the system, it is necessary to overlap different faculae that improve the target energy density. Hence, a novel method for incoherent combining of far-field laser beams is present. The method compromises piezoelectric ceramic technology and evaluation algorithm of faculae coincidence degree which based on high precision multi-channel optical path correction. The results show that the faculae recognition algorithm is low-latency(less than 10ms), which can meet the needs of practical engineering. Furthermore, the real time focusing ability of far field faculae is improved which was beneficial to the engineering of high-energy laser weapon or other laser jamming systems.

  18. Aspect sensitive E- and F-region SPEAR-enhanced incoherent backscatter observed by the EISCAT Svalbard radar

    Directory of Open Access Journals (Sweden)

    R. S. Dhillon

    2009-01-01

    Full Text Available Previous studies of the aspect sensitivity of heater-enhanced incoherent radar backscatter in the high-latitude ionosphere have demonstrated the directional dependence of incoherent scatter signatures corresponding to artificially excited electrostatic waves, together with consistent field-aligned signatures that may be related to the presence of artificial field-aligned irregularities. These earlier high-latitude results have provided motivation for repeating the investigation in the different geophysical conditions that obtain in the polar cap ionosphere. The Space Plasma Exploration by Active Radar (SPEAR facility is located within the polar cap and has provided observations of RF-enhanced ion and plasma line spectra recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR, which is collocated with SPEAR. In this paper, we present observations of aspect sensitive E- and F-region SPEAR-induced ion and plasma line enhancements that indicate excitation of both the purely growing mode and the parametric decay instability, together with sporadic E-layer results that may indicate the presence of cavitons. We note consistent enhancements from field-aligned, vertical and also from 5° south of field-aligned. We attribute the prevalence of vertical scatter to the importance of the Spitze region, and of that from field-aligned to possible wave/irregularity coupling.

  19. Improved BER based on intensity noise alleviation using developed detection technique for incoherent SAC-OCDMA systems

    Science.gov (United States)

    Al-Khafaji, Hamza M. R.; Aljunid, S. A.; Fadhil, Hilal A.

    2012-06-01

    The major drawback of incoherent spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems is their inherent intensity noise originating due to the incoherency of the broadband light sources. In this paper, we propose a developed detection technique named the modified-AND subtraction detection for incoherent SAC-OCDMA systems. This detection technique is based upon decreasing the received signal strength during the decoding process by dividing the spectrum of the utilized code sequence. The proposed technique is capable of mitigating the intensity noise effect, as well as suppressing the multiple-access interference impact. Based on modified quadratic congruence (MQC) code, the analytical results reveal that the modified-AND detection offer best bit-error rate (BER) performance and enables MQC code to support higher transmission rate up to 1.25 Gb/s compared to conventional AND detection. Furthermore, we ascertained that the proposed technique enhances the system performance using a simulation experiment.

  20. Theoretical and experimental studies of the influence of the number of crosstalk signals on the penalty caused by incoherent optical crosstalk

    DEFF Research Database (Denmark)

    Rasmussen, Christian Jørgen; Liu, Fenghai; Pedersen, Rune Johan Skullerud

    1999-01-01

    Calculations based on the exact probability density function of the received power show that for a fixed total crosstalk power, the incoherent crosstalk penalty increases with the number of crosstalk signals. Performed experiments verify this.......Calculations based on the exact probability density function of the received power show that for a fixed total crosstalk power, the incoherent crosstalk penalty increases with the number of crosstalk signals. Performed experiments verify this....

  1. Fluctuation-dissipation theorem in general relativity and the cosmological constant

    International Nuclear Information System (INIS)

    Mottola, E.

    1992-01-01

    Vacuum fluctuations are an essential feature of quantum field theory. Yet, the smallness of the scalar curvature of our universe suggests that the zero-point energy associated with these fluctuations does not curve spacetime. A possible way out of this paradox is suggested by the fact that microscopic fluctuations are generally accompanied by dissipative behavior in macroscopic systems. The intimate relation between the two is expressed by a fluctuation-dissipation theorem which extends to general relativity. The connection between quantum fluctuations and dissipation suggests a mechanism for the conversion of coherent stresses in the curvature of space into ordinary matter or radiation, thereby relaxing the effective cosmological ''constant'' to zero over time. The expansion of the universe may be the effect of this time-asymmetric relaxation process

  2. Analysis of dynamic multiplicity fluctuations at PHOBOS

    Science.gov (United States)

    Chai, Zhengwei; PHOBOS Collaboration; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Chai, Z.; Decowski, M. P.; García, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tang, J. L.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wuosmaa, A. H.; Wyslouch, B.

    2005-01-01

    This paper presents the analysis of the dynamic fluctuations in the inclusive charged particle multiplicity measured by PHOBOS for Au+Au collisions at surdsNN = 200GeV within the pseudo-rapidity range of -3 < η < 3. First the definition of the fluctuations observables used in this analysis is presented, together with the discussion of their physics meaning. Then the procedure for the extraction of dynamic fluctuations is described. Some preliminary results are included to illustrate the correlation features of the fluctuation observable. New dynamic fluctuations results will be available in a later publication.

  3. Thermal fluctuations in resonant motion of fluxons on a Josephson transmission line: Theory and experiment

    DEFF Research Database (Denmark)

    Jørgensen, E.; Koshelets, V. P.; Monaco, Roberto

    1982-01-01

    The radiation emission from long and narrow Josephson tunnel junctions dc-current biased on zero-field steps has been ascribed to resonant motion of fluxons on the transmission line. Within this dynamic model a theoretical expression for the radiation linewidth is derived from a full statistical ...... treatment of thermal fluctuations in the fluxon velocity. The result appears to be very general and is corroborated by experimental determination of linewidth and frequency of radiation emitted from overlap Nb-I-Pb junctions....

  4. Noise and fluctuations an introduction

    CERN Document Server

    MacDonald, D K C

    2006-01-01

    An understanding of fluctuations and their role is both useful and fundamental to the study of physics. This concise study of random processes offers graduate students and research physicists a survey that encompasses both the relationship of Brownian Movement with statistical mechanics and the problem of irreversible processes. It outlines the basics of the physics involved, without the strictures of mathematical rigor.The three-part treatment starts with a general survey of Brownian Movement, including electrical Brownian Movement and ""shot-noise,"" Part two explores correlation, frequency

  5. Electrostatic fluctuations in soap films

    International Nuclear Information System (INIS)

    Dean, D.S.; Horgan, R.R.

    2002-01-01

    A field theory to describe electrostatic interactions in soap films, described by electric multilayers with a generalized thermodynamic surface-charging mechanism, is studied. In the limit where the electrostatic interactions are weak, this theory is exactly soluble. The theory incorporates in a consistent way, the surface-charging mechanism and the fluctuations in the electrostatic field that correspond to the zero-frequency component of the van der Waals force. It is shown that these terms lead to a Casimir-like attraction that can be sufficiently large to explain the transition between the common black film to a Newton black film

  6. Chaotic fluctuations in mathematical economics

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Hiroyuki, E-mail: yoshida.hiroyuki@nihon-u.ac.jp [College of Economics, Nihon University, Chiyoda-ku, Tokyo 101-8360 (Japan)

    2011-03-01

    In this paper we examine a Cournot duopoly model, which expresses the strategic interaction between two firms. We formulate the dynamic adjustment process and investigate the dynamic properties of the stationary point. By introducing a memory mechanism characterized by distributed lag functions, we presuppose that each firm makes production decisions in a cautious manner. This implies that we have to deal with the system of integro-differential equations. By means of numerical simulations we show the occurrence of chaotic fluctuations in the case of fixed delays.

  7. An Objective Fluctuation Score for Parkinson's Disease

    Science.gov (United States)

    Horne, Malcolm K.; McGregor, Sarah; Bergquist, Filip

    2015-01-01

    Introduction Establishing the presence and severity of fluctuations is important in managing Parkinson’s Disease yet there is no reliable, objective means of doing this. In this study we have evaluated a Fluctuation Score derived from variations in dyskinesia and bradykinesia scores produced by an accelerometry based system. Methods The Fluctuation Score was produced by summing the interquartile range of bradykinesia scores and dyskinesia scores produced every 2 minutes between 0900-1800 for at least 6 days by the accelerometry based system and expressing it as an algorithm. Results This Score could distinguish between fluctuating and non-fluctuating patients with high sensitivity and selectivity and was significant lower following activation of deep brain stimulators. The scores following deep brain stimulation lay in a band just above the score separating fluctuators from non-fluctuators, suggesting a range representing adequate motor control. When compared with control subjects the score of newly diagnosed patients show a loss of fluctuation with onset of PD. The score was calculated in subjects whose duration of disease was known and this showed that newly diagnosed patients soon develop higher scores which either fall under or within the range representing adequate motor control or instead go on to develop more severe fluctuations. Conclusion The Fluctuation Score described here promises to be a useful tool for identifying patients whose fluctuations are progressing and may require therapeutic changes. It also shows promise as a useful research tool. Further studies are required to more accurately identify therapeutic targets and ranges. PMID:25928634

  8. Quantum fluctuations in beam dynamics

    International Nuclear Information System (INIS)

    Kim, K.-J.

    1998-01-01

    Quantum effects could become important for particle and photon beams used in high-luminosity and high brightness applications in the current and next generation accelerators and radiation sources. This paper is a review of some of these effects

  9. Currency speculation and dollar fluctuations

    Directory of Open Access Journals (Sweden)

    Stephan Schulmeister

    1988-12-01

    Full Text Available In this study the reasons behind the wide fluctuations of the dollar exchange rate following the breakdown of the Bretton Woods system, for the most part unexplained by the prevailing exchange rate theories, are explored. To do so, the author investigates the exchange rate between the two most traded currencies, the dollar and the deutschemark, from 1973 to 1988. In the first part, the pattern of the daily exchange rate movements is examined to show that a sequence of upward and downward trends interrupted by non-directional movements is typical of exchange rate dynamics in the short run. Moreover, this pattern is systemically exploited through currency speculation, particularly through the use of “technical analysis”. In the second part, the author focuses on the medium-term, arguing that fluctuations can be explained as the result of interacting disequilibria in the goods and asset markets. Although currency speculation has been systemically profitable for most currencies, it should be considered to be destabilizing since the sequence of price runs caused large and persistent deviations of exchange rates from their equilibrium values (purchasing power parity.

  10. Entropic fluctuations in DNA sequences

    Science.gov (United States)

    Thanos, Dimitrios; Li, Wentian; Provata, Astero

    2018-03-01

    The Local Shannon Entropy (LSE) in blocks is used as a complexity measure to study the information fluctuations along DNA sequences. The LSE of a DNA block maps the local base arrangement information to a single numerical value. It is shown that despite this reduction of information, LSE allows to extract meaningful information related to the detection of repetitive sequences in whole chromosomes and is useful in finding evolutionary differences between organisms. More specifically, large regions of tandem repeats, such as centromeres, can be detected based on their low LSE fluctuations along the chromosome. Furthermore, an empirical investigation of the appropriate block sizes is provided and the relationship of LSE properties with the structure of the underlying repetitive units is revealed by using both computational and mathematical methods. Sequence similarity between the genomic DNA of closely related species also leads to similar LSE values at the orthologous regions. As an application, the LSE covariance function is used to measure the evolutionary distance between several primate genomes.

  11. Universal bounds on current fluctuations.

    Science.gov (United States)

    Pietzonka, Patrick; Barato, Andre C; Seifert, Udo

    2016-05-01

    For current fluctuations in nonequilibrium steady states of Markovian processes, we derive four different universal bounds valid beyond the Gaussian regime. Different variants of these bounds apply to either the entropy change or any individual current, e.g., the rate of substrate consumption in a chemical reaction or the electron current in an electronic device. The bounds vary with respect to their degree of universality and tightness. A universal parabolic bound on the generating function of an arbitrary current depends solely on the average entropy production. A second, stronger bound requires knowledge both of the thermodynamic forces that drive the system and of the topology of the network of states. These two bounds are conjectures based on extensive numerics. An exponential bound that depends only on the average entropy production and the average number of transitions per time is rigorously proved. This bound has no obvious relation to the parabolic bound but it is typically tighter further away from equilibrium. An asymptotic bound that depends on the specific transition rates and becomes tight for large fluctuations is also derived. This bound allows for the prediction of the asymptotic growth of the generating function. Even though our results are restricted to networks with a finite number of states, we show that the parabolic bound is also valid for three paradigmatic examples of driven diffusive systems for which the generating function can be calculated using the additivity principle. Our bounds provide a general class of constraints for nonequilibrium systems.

  12. Fluctuations of the electron temperature measured by intensity interferometry on the W7-AS stellarator

    International Nuclear Information System (INIS)

    Sattler, S.

    1993-12-01

    Fluctuations of the electron temperature can cause a significant amount of the anomalous electron heat conductivity observed on fusion plasmas, even with relative amplitudes below one per cent. None of the standard diagnostics utilized for measuring the electron temperature in the confinement region of fusion plasmas is provided with sufficient spatial and temporal resolution and the sensitivity for small fluctuation amplitudes. In this work a new diagnostic for the measurement of electron temperature fluctuations in the confinement region of fusion plasmas was developed, built up, tested and successfully applied on the W7-AS Stellarator. Transport relevant fluctuations of the electron temperature can in principle be measured by radiometry of the electron cyclotron emission (ECE), but they might be buried completely in natural fluctuations of the ECE due to the thermal nature of this radiation. Fluctuations with relative amplitudes below one per cent can be measured with a temporal resolution in the μs-range and a spatial resolution of a few cm only with the help of correlation techniques. The intensity interferometry method, developed for radio astronomy, was applied here: two independent but identical radiometers are viewing the same emitting volume along crossed lines of sight. If the angle between the sightlines is chosen above a limiting value, which is determined by the spatial coherence properties of thermal radiation, the thermal noise is uncorrelated while the temperature fluctuations remain correlated. With the help of this technique relative amplitudes below 0.1% are accessible to measurement. (orig.)

  13. Intravoxel Incoherent Motion Metrics as Potential Biomarkers for Survival in Glioblastoma.

    Directory of Open Access Journals (Sweden)

    Josep Puig

    Full Text Available Intravoxel incoherent motion (IVIM is an MRI technique with potential applications in measuring brain tumor perfusion, but its clinical impact remains to be determined. We assessed the usefulness of IVIM-metrics in predicting survival in newly diagnosed glioblastoma.Fifteen patients with glioblastoma underwent MRI including spin-echo echo-planar DWI using 13 b-values ranging from 0 to 1000 s/mm2. Parametric maps for diffusion coefficient (D, pseudodiffusion coefficient (D*, and perfusion fraction (f were generated for contrast-enhancing regions (CER and non-enhancing regions (NCER. Regions of interest were manually drawn in regions of maximum f and on the corresponding dynamic susceptibility contrast images. Prognostic factors were evaluated by Kaplan-Meier survival and Cox proportional hazards analyses.We found that fCER and D*CER correlated with rCBFCER. The best cutoffs for 6-month survival were fCER>9.86% and D*CER>21.712 x10-3mm2/s (100% sensitivity, 71.4% specificity, 100% and 80% positive predictive values, and 80% and 100% negative predictive values; AUC:0.893 and 0.857, respectively. Treatment yielded the highest hazard ratio (5.484; 95% CI: 1.162-25.88; AUC: 0.723; P = 0.031; fCER combined with treatment predicted survival with 100% accuracy.The IVIM-metrics fCER and D*CER are promising biomarkers of 6-month survival in newly diagnosed glioblastoma.

  14. Intravoxel incoherent motion (IVIM) DWI of the liver. Pre-and postprandial comparison

    International Nuclear Information System (INIS)

    Hirose, Junji; Satou, Yuuichi; Amemiya, Ryoji; Yoda, Yoshioki; Motosugi, Utaroh

    2013-01-01

    We evaluated if meal intake changes the diffusivity result calculated using the intravoxel incoherent motion (IVIM) model and the portal flow velocity measured by phase contrast magnetic resonance (MR) imaging. We asked 3 healthy volunteers to eat 794-kcal meals and acquired MR images before and 20 minutes after the meal using a 1.5-tesla clinical MR scanner. We acquired 2-dimensional (2D) phase contrast (PC) gradient echo MR images to measure portal flow and diffusion-weighted images to calculate diffusivity results using the IVIM model and b-values of 0, 10, 20, 30, 40, 50, 70, 100, 200, 400, and 800 s/mm 2 . Portal flow was greater after the meal than (before): Volunteer A, 16.1 cm/s (9.7 cm/s); B, 18.0 cm/s (12.8 cm/s); and C, 18.3 cm/s (11.7 cm/s). The diffusivity results of D * and f were also increased after the meal in all 3 volunteers. D * and f values before and (after) the meal were: Volunteer A, 97.1 and 0.14 (149.6 and 0.20); Volunteer B, 79.4 and 0.20 (183.4 and 0.21); and Volunteer C, 29.4 and 0.19 (132.7 and 0.20). The trend in apparent diffusion coefficient (ADC) and D values were inconsistent among the 3 volunteers. The higher D * and f values in the liver after eating calculated using the IVIM model indicated increased portal flow due to the meal. (author)

  15. Intravoxel incoherent motion magnetic resonance imaging of the knee joint in children with juvenile idiopathic arthritis

    Energy Technology Data Exchange (ETDEWEB)

    Hilbert, Fabian; Sauer, Alexander; Koestler, Herbert [University Hospital Wuerzburg, Department of Diagnostic and Interventional Radiology, Wuerzburg (Germany); Holl-Wieden, Annette [University Hospital Wuerzburg, Department of Paediatrics, Wuerzburg (Germany); Neubauer, Henning [University Hospital Wuerzburg, Department of Diagnostic and Interventional Radiology, Wuerzburg (Germany); University Hospital Ulm, Department of Diagnostic and Interventional Radiology, Ulm (Germany)

    2017-05-15

    MRI of synovitis relies on use of a gadolinium-based contrast agent. Diffusion-weighted MRI (DWI) visualises thickened synovium but is of limited use in the presence of joint effusion. To investigate the feasibility and diagnostic accuracy of diffusion-weighted MRI with intravoxel incoherent motion (IVIM) for diagnosing synovitis in the knee joint of children with juvenile idiopathic arthritis. Twelve consecutive children with confirmed or suspected juvenile idiopathic arthritis (10 girls, median age 11 years) underwent MRI with contrast-enhanced T1-weighted imaging and DWI at 1.5 T. Read-out segmented multi-shot DWI was acquired at b values of 0 s/mm{sup 2}, 200 s/mm{sup 2}, 400 s/mm{sup 2} and 800 s/mm{sup 2}. We calculated the IVIM parameters perfusion fraction (f) and tissue diffusion coefficient (D). Diffusion-weighted images at b=800 s/mm{sup 2}, f parameter maps and post-contrast T1-weighted images were retrospectively assessed by two independent readers for synovitis using the Juvenile Arthritis MRI Scoring system. Seven (58%) children showed synovial hypertrophy on contrast-enhanced imaging. Diagnostic ratings for synovitis on DWI and on f maps were fully consistent with contrast-enhanced imaging, the diagnostic reference. Two children had equivocal low-confidence assessments on DWI. Median f was 6.7±2.0% for synovitis, 2.1±1.2% for effusion, 5.0±1.0% for muscle and 10.6±5.7% for popliteal lymph nodes. Diagnostic confidence was higher based on f maps in three (25%) children and lower in one child (8%), as compared to DWI. DWI with IVIM reliably visualises synovitis of the knee joint. Perfusion fraction maps differentiate thickened synovium from joint effusion and hence increase diagnostic confidence. (orig.)

  16. Feasibility of Intravoxel Incoherent Motion for Differentiating Benign and Malignant Thyroid Nodules.

    Science.gov (United States)

    Tan, Hui; Chen, Jun; Zhao, Yi Ling; Liu, Jin Huan; Zhang, Liang; Liu, Chang Sheng; Huang, Dongjie

    2018-06-13

    This study aimed to preliminarily investigate the feasibility of intravoxel incoherent motion (IVIM) theory in the differential diagnosis of benign and malignant thyroid nodules. Forty-five patients with 56 confirmed thyroid nodules underwent preoperative routine magnetic resonance imaging and IVIM diffusion-weighted imaging. The histopathologic diagnosis was confirmed by surgery. Apparent diffusion coefficient (ADC), perfusion fraction f, diffusivity D, and pseudo-diffusivity D* were quantified. Independent samples t test of IVIM-derived metrics were conducted between benign and malignant nodules. Receiver-operating characteristic analyses were performed to determine the optimal thresholds as well as the sensitivity and specificity for differentiating. Significant intergroup difference was observed in ADC, D, D*, and f (p < 0.001). Malignant tumors featured significantly lower ADC, D and D* values and a higher f value than that of benign nodules. The ADC, D, and D* could distinguish the benign from malignant thyroid nodules, and parameter f differentiate the malignant tumors from benign nodules. The values of the area under the curve for parameter ADC, D, and D* were 0.784 (p = 0.001), 0.795 (p = 0.001), and 0.850 (p < 0.001), separately, of which the area under the curve of f value was the maximum for identifying the malignant from benign nodules, which was 0.841 (p < 0.001). This study suggested that ADC and IVIM-derived metrics, including D, D*, and f, could potentially serve as noninvasive predictors for the preoperative differentiating of thyroid nodules, and f value performed best in identifying the malignant from benign nodules among these parameters. Copyright © 2018 Academic Radiology. Published by Elsevier Inc. All rights reserved.

  17. Comparison of the performance of different radar pulse compression techniques in an incoherent scatter radar measurement

    Directory of Open Access Journals (Sweden)

    B. Damtie

    2009-02-01

    Full Text Available Improving an estimate of an incoherent scatter radar signal is vital to provide reliable and unbiased information about the Earth's ionosphere. Thus optimizing the measurement spatial and temporal resolutions has attracted considerable attention. The optimization usually relies on employing different kinds of pulse compression filters in the analysis and a matched filter is perhaps the most widely used one. A mismatched filter has also been used in order to suppress the undesirable sidelobes that appear in the case of matched filtering. Moreover, recently an adaptive pulse compression method, which can be derived based on the minimum mean-square error estimate, has been proposed. In this paper we have investigated the performance of matched, mismatched and adaptive pulse compression methods in terms of the output signal-to-noise ratio (SNR and the variance and bias of the estimator. This is done by using different types of optimal radar waveforms. It is shown that for the case of low SNR the signal degradation associated to an adaptive filtering is less than that of the mismatched filtering. The SNR loss of both matched and adaptive pulse compression techniques was found to be nearly the same for most of the investigated codes for the case of high SNR. We have shown that the adaptive filtering technique is a compromise between matched and mismatched filtering method when one evaluates its performance in terms of the variance and the bias of the estimator. All the three analysis methods were found to have the same performance when a sidelobe-free matched filter code is employed.

  18. Comparison of the performance of different radar pulse compression techniques in an incoherent scatter radar measurement

    Directory of Open Access Journals (Sweden)

    B. Damtie

    2009-02-01

    Full Text Available Improving an estimate of an incoherent scatter radar signal is vital to provide reliable and unbiased information about the Earth's ionosphere. Thus optimizing the measurement spatial and temporal resolutions has attracted considerable attention. The optimization usually relies on employing different kinds of pulse compression filters in the analysis and a matched filter is perhaps the most widely used one. A mismatched filter has also been used in order to suppress the undesirable sidelobes that appear in the case of matched filtering. Moreover, recently an adaptive pulse compression method, which can be derived based on the minimum mean-square error estimate, has been proposed. In this paper we have investigated the performance of matched, mismatched and adaptive pulse compression methods in terms of the output signal-to-noise ratio (SNR and the variance and bias of the estimator. This is done by using different types of optimal radar waveforms. It is shown that for the case of low SNR the signal degradation associated to an adaptive filtering is less than that of the mismatched filtering. The SNR loss of both matched and adaptive pulse compression techniques was found to be nearly the same for most of the investigated codes for the case of high SNR. We have shown that the adaptive filtering technique is a compromise between matched and mismatched filtering method when one evaluates its performance in terms of the variance and the bias of the estimator. All the three analysis methods were found to have the same performance when a sidelobe-free matched filter code is employed.

  19. Hydrodynamical fluctuations in smooth shear flows

    International Nuclear Information System (INIS)

    Chagelishvili, G.D.; Khujadze, G.R.; Lominadze, J.G.

    1999-11-01

    Background of hydrodynamical fluctuations in a intrinsically/stochastically forced, laminar, uniform shear flow is studied. The employment of so-called nonmodal mathematical analysis makes it possible to represent the background of fluctuations in a new light and to get more insight into the physics of its formation. The basic physical processes responsible for the formation of vortex and acoustic wave fluctuation backgrounds are analyzed. Interplay of the processes at low and moderate shear rates is described. Three-dimensional vortex fluctuations around a given macroscopic state are numerically calculated. The correlation functions of the fluctuations of physical quantities are analyzed. It is shown that there exists subspace D k in the wave-number space (k-space) that is limited externally by spherical surface with radius k ν ≡ A/ν (where A is the velocity shear parameter, ν - the kinematic viscosity) in the nonequilibrium open system under study. The spatial Fourier harmonics of vortex as well as acoustic wave fluctuations are strongly subjected by flow shear (by the open character of the system) at wave-numbers satisfying the condition k ν . Specifically it is shown that in D k : The fluctuations are non-Markovian; the spatial spectral density of energy of the vortex fluctuations by far exceeds the white-noise; the term of a new type associated to the hydrodynamical fluctuation of velocity appears in the correlation function of pressure; the fluctuation background of the acoustic waves is completely different at low and moderate shear rates (at low shear rates it is reduced in D k in comparison to the uniform (non-shear) flow; at moderate shear rates it it comparable to the background of the vortex fluctuations). The fluctuation background of both the vortex and the acoustic wave modes is anisotropic. The possible significance of the fluctuation background of vortices for the subcritical transition to turbulence and Brownian motion of small macroscopic

  20. Stimulated coherent transition radiation

    International Nuclear Information System (INIS)

    Hung-chi Lihn.

    1996-03-01

    Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed

  1. Gravity waves from quantum stress tensor fluctuations in inflation

    International Nuclear Information System (INIS)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-01-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  2. Gravity waves from quantum stress tensor fluctuations in inflation

    Science.gov (United States)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-11-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  3. Lensing of 21-cm fluctuations by primordial gravitational waves.

    Science.gov (United States)

    Book, Laura; Kamionkowski, Marc; Schmidt, Fabian

    2012-05-25

    Weak-gravitational-lensing distortions to the intensity pattern of 21-cm radiation from the dark ages can be decomposed geometrically into curl and curl-free components. Lensing by primordial gravitational waves induces a curl component, while the contribution from lensing by density fluctuations is strongly suppressed. Angular fluctuations in the 21-cm background extend to very small angular scales, and measurements at different frequencies probe different shells in redshift space. There is thus a huge trove of information with which to reconstruct the curl component of the lensing field, allowing tensor-to-scalar ratios conceivably as small as r~10(-9)-far smaller than those currently accessible-to be probed.

  4. Fluctuating hyperfine interactions: computational implementation

    International Nuclear Information System (INIS)

    Zacate, M. O.; Evenson, W. E.

    2010-01-01

    A library of computational routines has been created to assist in the analysis of stochastic models of hyperfine interactions. We call this library the stochastic hyperfine interactions modeling library (SHIML). It provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental hyperfine interaction measurements can be calculated. Example model calculations are included in the SHIML package to illustrate its use and to generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A 22 can be neglected.

  5. Fluctuating nonlinear hydrodynamics of flocking

    Science.gov (United States)

    Yadav, Sunil Kumar; Das, Shankar P.

    2018-03-01

    Starting from a microscopic model, the continuum field theoretic description of the dynamics of a system of active ingredients or "particles" is presented. The equations of motion for the respective collective densities of mass and momentum follow exactly from that of a single element in the flock. The single-particle dynamics has noise and anomalous momentum dependence in its frictional terms. The equations for the collective densities are averaged over a local equilibrium distribution to obtain the corresponding coarse grained equations of fluctuating nonlinear hydrodynamics (FNH). The latter are the equations used frequently for describing active systems on the basis of intuitive arguments. The transport coefficients which appear in the macroscopic FNH equations are determined in terms of the parameters of the microscopic dynamics.

  6. Interplanetary Alfvenic fluctuations: A stochastic model

    International Nuclear Information System (INIS)

    Barnes, A.

    1981-01-01

    The strong alignment of the average directions of minimum magnetic variance and mean magnetic field in interplanetary Alfvenic fluctuations is inconsistent with the usual wave-propagation models. We investigate the concept of minimum variance for nonplanar Alfvenic fluctuations in which the field direction varies stochastically. It is found that the tendency of the minimum variance and mean field directions to be aligned may be purely a consequence of the randomness of the field direction. In particular, a well-defined direction of minimum variance does not imply that the fluctuations are necessarily planar. The fluctuation power spectrum is a power law for frequencies much higher than the inverse of the correlation time. The probability distribution of directions a randomly fluctuating field of constant magnitude is calculated. A new approach for observational studies of interplanetary fluctuations is suggested

  7. Efficiency of the scattered primary radiation as an internal standard in the determination of uranium and thorium in geological materials by X-ray spectrometry

    International Nuclear Information System (INIS)

    Diaz-Guerra, J.P.; Bayon, A.

    1980-01-01

    The efficiency of the scattered primary coherent and incoherent X-radiation of various wavelengths has been studied as a matrix correction in the determination of uranium and thorium in geological materials by X-ray spectrometry. The excitation has been performed with molybdenum and tungsten targets. Results illustrate that the incoherently-scattered Mok βsub(1,3) and Mok βsub(1,2) radiation are, respectively, the optimum reference lines. The particle size influence and the critical thickness of the sample are also considered.(auth.)

  8. Recent results of studies of plasma fluctuations in stellarators by microwave scattering technique

    International Nuclear Information System (INIS)

    Skvortsova, N.N.; Batanov, G.M.; Kolik, L.V.; Petrov, A.E.; Pshenichnikov, A.A.; Sarksyan, K.A.; Kharchev, N.K.; Khol'nov, Yu.V.; Kubo, S.; Sanchez, J.

    2005-01-01

    Microwave scattering diagnostics are described that allow direct measurements of the turbulent processes in a high-temperature plasma of magnetic confinement systems. Plasma density fluctuations in the heating region of the L-2M stellarator were measured from microwave scattering at the fundamental and the second harmonics of the heating gyrotron radiation. In the TJ-II stellarator, a separate 2-mm microwave source was used to produce a probing beam; the measurements were performed at the middle of the plasma radius. Plasma density fluctuations in the axial (heating) region of the LHD stellarator were measured from microwave scattering at the fundamental harmonic of the heating gyrotron radiation. Characteristic features of fluctuations, common for all three devices, are revealed with the methods of statistical and spectral analysis. These features are the wide frequency Fourier and wavelet spectra, autocorrelation functions with slowly decreasing tails, and non-Gaussian probability distributions of the magnitudes and the increments of the magnitude of fluctuations. The drift-dissipative instability and the instability driven by trapped electrons are examined as possible sources of turbulence in a high-temperature plasma. Observations showed the high level of coherence between turbulent fluctuations in the central region and at the edge of the plasma in L-2M. It is shown in L-2M that the relative intensity of the second harmonic of gyrotron radiation on the axis of a microwave beam after quasi-optical filtering in a four-mirror quasi-optical transmission line is about -50 dB of the total radiation intensity. Spatiotemporal structures in plasma density fluctuations were observed in the central region of the plasma column. The correlation time between the structures was found to be on the order of 1 ms. It is shown that, the spectrum of the signal from the second-harmonic scattering extends to higher frequencies in comparison with that from the fundamental

  9. Wind fluctuations over the North Sea

    DEFF Research Database (Denmark)

    Vincent, Claire Louise; Pinson, Pierre; Giebel, Gregor

    2011-01-01

    Climatological patterns in wind speed fluctuations with periods of 1 min to 10 h are analysed using data from a meteorological mast in the Danish North Sea. Fluctuations on these time scales are of particular relevance to the effective management of the power supply from large wind farms. The Hil......Climatological patterns in wind speed fluctuations with periods of 1 min to 10 h are analysed using data from a meteorological mast in the Danish North Sea. Fluctuations on these time scales are of particular relevance to the effective management of the power supply from large wind farms...

  10. Neutrino propagation in a fluctuating sun

    International Nuclear Information System (INIS)

    Burgess, C.P.; Michaud, D.

    1997-01-01

    We adapt to neutrino physics a general formulation for particle propagation in fluctuating media, initially developed for applications to electromagnetism and neutron optics. In leading approximation this formalism leads to the usual MSW effective Hamiltonian governing neutrino propagation through a medium. Next-to-leading contributions describe deviations from this description, which arise due to neutrino interactions with fluctuations in the medium. We compute these corrections for two types of fluctuations: (i) microscopic thermal fluctuations and (ii) macroscopic fluctuations in the medium s density. While the first of these reproduces standard estimates, which are negligible for applications to solar neutrinos, we find that the second can be quite large, since it grows in size with the correlation length of the fluctuation. We consider two models in some detail. For fluctuations whose correlations extend only over a local region in space of length l, appreciable effects for MSW oscillations arise if (δn/n) 2 l approx-gt 100m or so. Alternatively, a crude model of helioseismic p-waves gives appreciable effects only when (δn/n)approx-gt 1%. In general the dominant effect is to diminish the quality of the resonance, making the suppression of the 7 Be neutrinos a good experimental probe of fluctuations deep within the sun. Fluctuations can also provide a new mechanism for reducing the solar neutrino flux, giving an energy-independent suppression factor of 1/2 away from the resonant region, even for small vacuum mixing angles. copyright 1997 Academic Press, Inc

  11. Non-Gaussian conductivity fluctuations in semiconductors

    International Nuclear Information System (INIS)

    Melkonyan, S.V.

    2010-01-01

    A theoretical study is presented on the statistical properties of conductivity fluctuations caused by concentration and mobility fluctuations of the current carriers. It is established that mobility fluctuations result from random deviations in the thermal equilibrium distribution of the carriers. It is shown that mobility fluctuations have generation-recombination and shot components which do not satisfy the requirements of the central limit theorem, in contrast to the current carrier's concentration fluctuation and intraband component of the mobility fluctuation. It is shown that in general the mobility fluctuation consist of thermal (or intraband) Gaussian and non-thermal (or generation-recombination, shot, etc.) non-Gaussian components. The analyses of theoretical results and experimental data from literature show that the statistical properties of mobility fluctuation and of 1/f-noise fully coincide. The deviation from Gaussian statistics of the mobility or 1/f fluctuations goes hand in hand with the magnitude of non-thermal noise (generation-recombination, shot, burst, pulse noises, etc.).

  12. On the role of impurity radiation on edge turbulence in the TJ-1 Tokamak

    International Nuclear Information System (INIS)

    Ochando, M.A.; Pedrosa, M.A.; Balbin, R.; Garcia-Cortes, I.; Hidalgo, C.

    1994-01-01

    The correlation between edge radiation and electron temperature and density fluctuations has been studied in the vicinity of the upper poloidal limiter of the TJ-I tokamak. When edge impurity radiation is strongly raked in the proximity of the limiter radius, electron temperature fluctuations are notably higher than density fluctuations. Results provide experimental evidence of edge turbulence driven by thermal instabilities

  13. Incoherent scattering functions of 145 keV gamma rays by K-shell electrons in Y, Ag and Au

    International Nuclear Information System (INIS)

    Raghava Rao, A.; Ramana Reddy, S.V.S.; Premchand, K.; Narasimham, K.L.; Parthasaradhi, K.; Lakshminarayana, V.

    1982-01-01

    The values of incoherent scattering functions are determined experimentally for 145 keV gamma rays in elements Au, Ag and Y at scattering angles 40 0 , 70 0 and 100 0 , using a x-ray gamma coincidence technique. The corresponding theoretical values are obtained from the tabulations of Hubbell et al, and computed from the models of Jauch and Rohrlich and Shimizu et al. A comparison between the theoretical and experimental results showed that the non-relativistic approach adopted in the theory of Shimizu et al is inapplicable to the present cases. A gross agreement is noticed between the present experimental results and the other theoretical values. (author)

  14. Neutrino-nucleus cross-sections: a unified theoretical approach for nucleon knock-out, coherent and incoherent pion production

    CERN Document Server

    Martini, M; G. Chanfray; Marteau, J

    2010-01-01

    Neutrino-nucleus cross-sections are needed to interpret neutrino oscillation data, as neutrino detectors involve complex nuclei. We present a theory of neutrino interactions with nuclei aimed at a unified description of the partial cross-sections, namely quasi-elastic and multi-nucleon emission, coherent and incoherent single pion production. We compare our approach to the available neutrino experimental data on carbon. We also discuss the evolution of the neutrino cross-sections with the mass number in view of future precision ex- periments which will use a liquid argon chamber.

  15. Use of intravoxel incoherent motion diffusion-weighted imaging to detect early changes in diabetic kidneys.

    Science.gov (United States)

    Deng, Yi; Yang, Biran; Peng, Yan; Liu, Zhiqiang; Luo, Jinwen; Du, Guoxin

    2018-03-14

    The purpose of the study was to examine differences in kidney intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) parameters in early-stage diabetic patients versus healthy controls. Nineteen type 2 diabetic patients (group A) with a urinary albumin-to-creatinine ratio (ACR) diabetic kidney changes was determined by receiver operating characteristic analysis. Three radiologists independently measured the parameters derived from IVIM-DWI in the two groups by free-hand placing regions of interest, and the interclass coefficients (ICCs) were analyzed by SPSS.16.0 software. The f values of the kidneys were significantly higher in diabetic patients than in healthy volunteers. The D value of the kidneys was significantly lower in diabetic patients than in healthy volunteers. No significant differences in the D* values of the kidneys were observed between diabetic patients and healthy volunteers. The D values of the right kidneys were significantly higher than those of the left kidneys in both groups. The results of the receiver operating characteristic analysis were as follows: left kidney-f value AUC = 0.650 (cutoff point ≥ 27.49%) and D value AUC = 0.752 (cutoff point ≤ 1.68 × 10 -3  mm 2 /s); and right kidney-f value AUC = 0.650 (cutoff point ≥ 28.24%) and D value AUC = 0.752 (cutoff point ≤ 1.81 × 10 -3 mm 2 /s). The diagnostic performance of the D* value was very low (AUC  0.05). The ICCs of the f value and D value were between 0.637 and 0.827. The ICC of the D* value was less than 0.3. The results of our study suggest that changes in kidneys detected by IVIM-DWI may serve as indicators of early diabetic kidney disease.

  16. Intravoxel incoherent motion diffusion-weighted imaging in stroke patients: initial clinical experience

    International Nuclear Information System (INIS)

    Yao, Y.; Zhang, S.; Tang, X.; Zhang, S.; Shi, J.; Zhu, W.; Zhu, W.

    2016-01-01

    Aim: To evaluate the feasibility of using intravoxel incoherent motion (IVIM) to measure diffusion and perfusion parameter variations in stroke. Materials and methods: Thirty-eight stroke patients were enrolled in the study. IVIM imaging was performed using 15 b-values from 0 to 1000 s/mm"2. Arterial spin labelling (ASL) magnetic resonance perfusion was also undertaken. Relations between the IVIM parameters (including apparent diffusion coefficient [ADC], diffusion coefficient D_s_l_o_w [D], pseudo-diffusion coefficient D_f_a_s_t [D*], fractional perfusion-related volume [f]) and fD* (the multiplication of the first two parameters) and the ASL-derived parameter, cerebral blood flow (CBF), were analysed using paired t-tests. Comparisons of all the parameters between lesions and contralateral normal regions, as well as between acute and subacute groups were analysed using Student's t-test. Results: There were positive correlations between f and CBF as well as fD* and CBF (r=0.472 and 0.653). Quantitative analysis showed a significant decrease in ADC, D, D*, f, fD*, and CBF of the lesions compared with the contralateral side, in which the decrease of fD* (68.6%) was highest. The values of ADC, f, and fD* increased in the subacute period group compared with the acute period group. Conclusions: IVIM analysis allowed separation of perfusion contribution from true diffusion and thus provided an evaluation of the perfusion and diffusion variations during stroke, which might further elucidate the mechanisms of ischaemic stroke. - Highlights: • There exist positive correlations between fractional perfusion-related volume (f) and cerebral blood flow (CBF) as well as fD"∗ and CBF. • A significant decrease in ADC, diffusion coefficient D_s_l_o_w (D), pseudo-diffusion coefficient D_f_a_s_t (D"∗), f, fD"∗ and CBF of the lesions compared with the contralateral normal regions. • The values of ADC, f and fD"∗ increase significantly in the subacute period compared with

  17. Using the Flipchem Photochemistry Model When Fitting Incoherent Scatter Radar Data

    Science.gov (United States)

    Reimer, A. S.; Varney, R. H.

    2017-12-01

    The North face Resolute Bay Incoherent Scatter Radar (RISR-N) routinely images the dynamics of the polar ionosphere, providing measurements of the plasma density, electron temperature, ion temperature, and line of sight velocity with seconds to minutes time resolution. RISR-N does not directly measure ionospheric parameters, but backscattered signals, recording them as voltage samples. Using signal processing techniques, radar autocorrelation functions (ACF) are estimated from the voltage samples. A model of the signal ACF is then fitted to the ACF using non-linear least-squares techniques to obtain the best-fit ionospheric parameters. The signal model, and therefore the fitted parameters, depend on the ionospheric ion composition that is used [e.g. Zettergren et. al. (2010), Zou et. al. (2017)].The software used to process RISR-N ACF data includes the "flipchem" model, which is an ion photochemistry model developed by Richards [2011] that was adapted from the Field LineInterhemispheric Plasma (FLIP) model. Flipchem requires neutral densities, neutral temperatures, electron density, ion temperature, electron temperature, solar zenith angle, and F10.7 as inputs to compute ion densities, which are input to the signal model. A description of how the flipchem model is used in RISR-N fitting software will be presented. Additionally, a statistical comparison of the fitted electron density, ion temperature, electron temperature, and velocity obtained using a flipchem ionosphere, a pure O+ ionosphere, and a Chapman O+ ionosphere will be presented. The comparison covers nearly two years of RISR-N data (April 2015 - December 2016). Richards, P. G. (2011), Reexamination of ionospheric photochemistry, J. Geophys. Res., 116, A08307, doi:10.1029/2011JA016613.Zettergren, M., Semeter, J., Burnett, B., Oliver, W., Heinselman, C., Blelly, P.-L., and Diaz, M.: Dynamic variability in F-region ionospheric composition at auroral arc boundaries, Ann. Geophys., 28, 651-664, https

  18. Occurrence rate of ion upflow and downflow observed by the Poker Flat Incoherent Scatter Radar (PFISR)

    Science.gov (United States)

    Zou, S.; Lu, J.; Varney, R. H.

    2017-12-01

    This study aims to investigate the occurrence rate of ion upflow and downflow events in the auroral ionosphere, using a full 3-year (2011-2013) dataset collected by the Poker Flat Incoherent Scatter Radar (PFISR) at 65.5° magnetic latitude. Ion upflow and downflow events are defined if there are three consecutive data points larger/smaller than 100/-100 m/s in the ion field-aligned velocity altitude profile. Their occurrence rates have been evaluated as a function of magnetic local time (MLT), season, geomagnetic activity, solar wind and interplanetary magnetic field (IMF). We found that the ion upflows are twice more likely to occur on the nightside than the dayside, and have slightly higher occurrence rate near Fall equinox. In contrast, the ion downflow events are more likely to occur in the afternoon sector but also during Fall equinox. In addition, the occurrence rate of ion upflows on the nightside increases when the aurora electrojet index (AE) and planetary K index (Kp) increase, while the downflows measured on the dayside clearly increase as the AE and Kp increase. In general, the occurrence rate of ion upflows increases with enhanced solar wind and IMF drivers. This correlation is particularly strong between the upflows on the nightside and the solar wind dynamic pressure and IMF Bz. The lack of correlation of upflows on the dayside with these parameters is due to the location of PFISR, which is usually equatorward of the dayside auroral zone and within the nightside auroral zone under disturbed conditions. The occurrence rate of downflow at all MLTs does not show strong dependence on the solar wind and IMF conditions. However, it occurs much more frequently on the dayside when the IMF By is strongly positive, i.e., >10 nT and the IMF Bz is strongly negative, i.e., < -10 nT. We suggest that the increased occurrence rate of downflows on the dayside is associated with dayside storm-enhanced density and the plume.

  19. Assessment of cervical cancer with a parameter-free intravoxel incoherent motion imaging algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Anton S.; Wurnig, Moritz C.; Boss, Andreas; Ghafoor, Soleen [Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, Zurich (Switzerland); Perucho, Jose A.; Khong, Pek Lan; Lee, Elaine Y. P. [Dept. of Diagnostic Radiology, The University of Hong Kong, Hong Kong (China)

    2017-06-15

    To evaluate the feasibility of a parameter-free intravoxel incoherent motion (IVIM) approach in cervical cancer, to assess the optimal b-value threshold, and to preliminarily examine differences in the derived perfusion and diffusion parameters for different histological cancer types. After Institutional Review Board approval, 19 female patients (mean age, 54 years; age range, 37–78 years) gave consent and were enrolled in this prospective magnetic resonance imaging study. Clinical staging and biopsy results were obtained. Echo-planar diffusion weighted sequences at 13 b-values were acquired at 3 tesla field strength. Single-sliced region-of-interest IVIM analysis with adaptive b-value thresholds was applied to each tumor, yielding the optimal fit and the optimal parameters for pseudodiffusion (D*), perfusion fraction (Fp) and diffusion coefficient (D). Monoexponential apparent diffusion coefficient (ADC) was calculated for comparison with D. Biopsy revealed squamous cell carcinoma in 10 patients and adenocarcinoma in 9. The b-value threshold (median [interquartile range]) depended on the histological type and was 35 (22.5–50) s/mm{sup 2} in squamous cell carcinoma and 150 (100–150) s/mm{sup 2} in adenocarcinoma (p < 0.05). Comparing squamous cell vs. adenocarcinoma, D* (45.1 [25.1–60.4] × 10{sup −3} mm{sup 2}/s vs. 12.4 [10.5–21.2] × 10{sup −3} mm{sup 2}/s) and Fp (7.5% [7.0–9.0%] vs. 9.9% [9.0–11.4%]) differed significantly between the subtypes (p < 0.02), whereas D did not (0.89 [0.75–0.94] × 10{sup −3} mm{sup 2}/s vs. 0.90 [0.82–0.97] × 10{sup −3} mm{sup 2}/s, p = 0.27). The residuals did not differ (0.74 [0.60–0.92] vs. 0.94 [0.67–1.01], p = 0.32). The ADC systematically underestimated the magnitude of diffusion restriction compared to D (p < 0.001). The parameter-free IVIM approach is feasible in cervical cancer. The b-value threshold and perfusion-related parameters depend on the tumor histology type.

  20. Storm/Quiet Ratio Comparisons Between TIMED/SABER NO (sup +)(v) Volume Emission Rates and Incoherent Scatter Radar Electron Densities at E-Region Altitudes

    Science.gov (United States)

    Fernandez, J. R.; Mertens, C. J.; Bilitza, D.; Xu, X.; Russell, J. M., III; Mlynczak, M. G.

    2009-01-01

    Broadband infrared limb emission at 4.3 microns is measured by the TIMED/SABER instrument. At night, these emission observations at E-region altitudes are used to derive the so called NO+(v) Volume Emission Rate (VER). NO+(v) VER can be derived by removing the background CO2(v3) 4.3 microns radiance contribution using SABER-based non-LTE radiation transfer models, and by performing a standard Abel inversion on the residual radiance. SABER observations show that NO+(v) VER is significantly enhanced during magnetic storms in accordance with increased ionization of the neutral atmosphere by auroral electron precipitation, followed by vibrational excitation of NO+ (i.e., NO+(v)) from fast exothermic ion-neutral reactions, and prompt infrared emission at 4.3 m. Due to charge neutrality, the NO+(v) VER enhancements are highly correlated with electron density enhancements, as observed for example by Incoherent Scatter Radar (ISR). In order to characterize the response of the storm-time E-region from both SABER and ISR measurements, a Storm/Quiet ratio (SQR) quantity is defined as a function of altitude. For SABER, the SQR is the ratio of the storm-to-quiet NO+(v) VER. SQR is the storm-to-quiet ratio of electron densities for ISR. In this work, we compare SABER and ISR SQR values between 100 to 120 km. Results indicate good agreement between these measurements. SQR values are intended to be used as a correction factor to be included in an empirical storm-time correction to the International Reference Ionosphere model at E-region altitudes.

  1. Intravoxel Incoherent Motion MR Imaging in the Differentiation of Benign and Malignant Sinonasal Lesions: Comparison with Conventional Diffusion-Weighted MR Imaging.

    Science.gov (United States)

    Xiao, Z; Tang, Z; Qiang, J; Wang, S; Qian, W; Zhong, Y; Wang, R; Wang, J; Wu, L; Tang, W; Zhang, Z

    2018-01-25

    Intravoxel incoherent motion is a promising method for the differentiation of sinonasal lesions. This study aimed to evaluate the value of intravoxel incoherent motion in the differentiation of benign and malignant sinonasal lesions and to compare the diagnostic performance of intravoxel incoherent motion with that of conventional DWI. One hundred thirty-one patients with histologically proved solid sinonasal lesions (56 benign and 75 malignant) who underwent conventional DWI and intravoxel incoherent motion were recruited in this study. The diffusion coefficient ( D ), pseudodiffusion coefficient ( D *), and perfusion fraction ( f ) values derived from intravoxel incoherent motion and ADC values derived from conventional DWI were measured and compared between the 2 groups using the Student t test. Receiver operating characteristic curve analysis, logistic regression analysis, and 10-fold cross-validation were performed to evaluate the diagnostic performance of single-parametric and multiparametric models. The mean ADC and D values were significantly lower in malignant sinonasal lesions than in benign sinonasal lesions (both P benign and malignant sinonasal lesions. © 2018 by American Journal of Neuroradiology.

  2. New aspects of the casimir effect: Fluctuations and radiative reaction

    International Nuclear Information System (INIS)

    Barton, G.

    1994-01-01

    But since I am among equally irrational men, I won't be criticized I hope for the fact that there is no possible, practical reason for making these calculations....We all realize that no matter how small a thing is, if it has physical interest and is thought about carefully enough, your're bound to think of something that's good for something else. 48 refs

  3. Radiation Transport in Random Media With Large Fluctuations

    Science.gov (United States)

    Olson, Aaron; Prinja, Anil; Franke, Brian

    2017-09-01

    Neutral particle transport in media exhibiting large and complex material property spatial variation is modeled by representing cross sections as lognormal random functions of space and generated through a nonlinear memory-less transformation of a Gaussian process with covariance uniquely determined by the covariance of the cross section. A Karhunen-Loève decomposition of the Gaussian process is implemented to effciently generate realizations of the random cross sections and Woodcock Monte Carlo used to transport particles on each realization and generate benchmark solutions for the mean and variance of the particle flux as well as probability densities of the particle reflectance and transmittance. A computationally effcient stochastic collocation method is implemented to directly compute the statistical moments such as the mean and variance, while a polynomial chaos expansion in conjunction with stochastic collocation provides a convenient surrogate model that also produces probability densities of output quantities of interest. Extensive numerical testing demonstrates that use of stochastic reduced-order modeling provides an accurate and cost-effective alternative to random sampling for particle transport in random media.

  4. A high pressure study of calmodulin-ligand interactions using small-angle X-ray and elastic incoherent neutron scattering.

    Science.gov (United States)

    Cinar, Süleyman; Al-Ayoubi, Samy; Sternemann, Christian; Peters, Judith; Winter, Roland; Czeslik, Claus

    2018-01-31

    Calmodulin (CaM) is a Ca 2+ sensor and mediates Ca 2+ signaling through binding of numerous target ligands. The binding of ligands by Ca 2+ -saturated CaM (holo-CaM) is governed by attractive hydrophobic and electrostatic interactions that are weakened under high pressure in aqueous solutions. Moreover, the potential formation of void volumes upon ligand binding creates a further source of pressure sensitivity. Hence, high pressure is a suitable thermodynamic variable to probe protein-ligand interactions. In this study, we compare the binding of two different ligands to holo-CaM as a function of pressure by using X-ray and neutron scattering techniques. The two ligands are the farnesylated hypervariable region (HVR) of the K-Ras4B protein, which is a natural binding partner of holo-CaM, and the antagonist trifluoperazine (TFP), which is known to inhibit holo-CaM activity. From small-angle X-ray scattering experiments performed up to 3000 bar, we observe a pressure-induced partial unfolding of the free holo-CaM in the absence of ligands, where the two lobes of the dumbbell-shaped protein are slightly swelled. In contrast, upon binding TFP, holo-CaM forms a closed globular conformation, which is pressure stable at least up to 3000 bar. The HVR of K-Ras4B shows a different binding behavior, and the data suggest the dissociation of the holo-CaM/HVR complex under high pressure, probably due to a less dense protein contact of the HVR as compared to TFP. The elastic incoherent neutron scattering experiments corroborate these findings. Below 2000 bar, pressure induces enhanced atomic fluctuations in both holo-CaM/ligand complexes, but those of the holo-CaM/HVR complex seem to be larger. Thus, the inhibition of holo-CaM by TFP is supported by a low-volume ligand binding, albeit this is not associated with a rigidification of the complex structure on the sub-ns Å-scale.

  5. Modeling of fluctuating reaction networks

    International Nuclear Information System (INIS)

    Lipshtat, A.; Biham, O.

    2004-01-01

    Full Text:Various dynamical systems are organized as reaction networks, where the population size of one component affects the populations of all its neighbors. Such networks can be found in interstellar surface chemistry, cell biology, thin film growth and other systems. I cases where the populations of reactive species are large, the network can be modeled by rate equations which provide all reaction rates within mean field approximation. However, in small systems that are partitioned into sub-micron size, these populations strongly fluctuate. Under these conditions rate equations fail and the master equation is needed for modeling these reactions. However, the number of equations in the master equation grows exponentially with the number of reactive species, severely limiting its feasibility for complex networks. Here we present a method which dramatically reduces the number of equations, thus enabling the incorporation of the master equation in complex reaction networks. The method is examplified in the context of reaction network on dust grains. Its applicability for genetic networks will be discussed. 1. Efficient simulations of gas-grain chemistry in interstellar clouds. Azi Lipshtat and Ofer Biham, Phys. Rev. Lett. 93 (2004), 170601. 2. Modeling of negative autoregulated genetic networks in single cells. Azi Lipshtat, Hagai B. Perets, Nathalie Q. Balaban and Ofer Biham, Gene: evolutionary genomics (2004), In press

  6. Measuring shape fluctuations in biological membranes

    International Nuclear Information System (INIS)

    Monzel, C; Sengupta, K

    2016-01-01

    Shape fluctuations of lipid membranes have intrigued cell biologists and physicists alike. In the cellular context, their origin—thermal or active—and their physiological significance are open questions. These small incessant displacements, also called membrane undulations, have mostly been studied in model membranes and membranes of simple cells like erythrocytes. Thermal fluctuations of such membranes have been very well described both theoretically and experimentally; active fluctuations are a topic of current interest. Experimentally, membrane fluctuations are not easy to measure, the main challenge being to develop techniques which are capable of measuring very small displacements at very high speed, and preferably over a large area and long time. Scattering techniques have given access to fluctuations in membrane stacks and a variety of optical microscopy based techniques have been devised to study membrane fluctuations of unilamellar vesicles, erythrocytes and other cells. Among them are flicker spectroscopy, dynamic light scattering, diffraction phase microscopy and reflection interference contrast microscopy. Each of these techniques has its advantages and limitations. Here we review the basic principles of the major experimental techniques used to measure bending or shape fluctuations of biomembranes. We report seminal results obtained with each technique and highlight how these studies furthered our understanding of physical properties of membranes and their interactions. We also discuss suggested role of membrane fluctuations in different biological processes. (topical review)

  7. Sources of Macroeconomic Fluctuations in MENA Countries

    OpenAIRE

    Balcilar, Mehmet; Bagzibagli, Kemal

    2010-01-01

    A close examination of the MENA region economies reveals a number of fundamental sources of macroeconomic fluctuations. These include economic factors such as exchange rate instability, large public debt, current account deficits, and escalation of inflation. The political factors such as government instability, corruption, bureaucracy, and internal conflicts also are major sources of macroeconomic instability. Thus, the sources of macroeconomic fluctuations in these countri...

  8. The Spectrum of Wind Power Fluctuations

    Science.gov (United States)

    Bandi, Mahesh

    2016-11-01

    Wind is a variable energy source whose fluctuations threaten electrical grid stability and complicate dynamical load balancing. The power generated by a wind turbine fluctuates due to the variable wind speed that blows past the turbine. Indeed, the spectrum of wind power fluctuations is widely believed to reflect the Kolmogorov spectrum; both vary with frequency f as f - 5 / 3. This variability decreases when aggregate power fluctuations from geographically distributed wind farms are averaged at the grid via a mechanism known as geographic smoothing. Neither the f - 5 / 3 wind power fluctuation spectrum nor the mechanism of geographic smoothing are understood. In this work, we explain the wind power fluctuation spectrum from the turbine through grid scales. The f - 5 / 3 wind power fluctuation spectrum results from the largest length scales of atmospheric turbulence of order 200 km influencing the small scales where individual turbines operate. This long-range influence spatially couples geographically distributed wind farms and synchronizes farm outputs over a range of frequencies and decreases with increasing inter-farm distance. Consequently, aggregate grid-scale power fluctuations remain correlated, and are smoothed until they reach a limiting f - 7 / 3 spectrum. This work was funded by the Collective Interactions Unit, OIST Graduate University, Japan.

  9. Intrinsic intensity fluctuations in random lasers

    International Nuclear Information System (INIS)

    Molen, Karen L. van der; Mosk, Allard P.; Lagendijk, Ad

    2006-01-01

    We present a quantitative experimental and theoretical study of intensity fluctuations in the emitted light of a random laser that has different realizations of disorder for every pump pulse. A model that clarifies these intrinsic fluctuations is developed. We describe the output versus input power graphs of the random laser with an effective spontaneous emission factor (β factor)

  10. Fluctuations of offshore wind generation: Statistical modelling

    DEFF Research Database (Denmark)

    Pinson, Pierre; Christensen, Lasse E.A.; Madsen, Henrik

    2007-01-01

    The magnitude of power fluctuations at large offshore wind farms has a significant impact on the control and management strategies of their power output. If focusing on the minute scale, one observes successive periods with smaller and larger power fluctuations. It seems that different regimes yi...

  11. Multi moment cancellation of participant fluctuations

    OpenAIRE

    Begun, Viktor; Mackowiak-Pawlowska, Maja

    2017-01-01

    We summarize the new method for the correction of participant fluctuations in high energy nucleus-nucleus collisions. It allows to estimate a fluctuation baseline in comparison to a useful signal. In particular cases of a weak signal compared to baseline, it allows to cancel the baseline contribution from participants.

  12. Long-range correlation in cosmic microwave background radiation.

    Science.gov (United States)

    Movahed, M Sadegh; Ghasemi, F; Rahvar, Sohrab; Tabar, M Reza Rahimi

    2011-08-01

    We investigate the statistical anisotropy and gaussianity of temperature fluctuations of Cosmic Microwave Background (CMB) radiation data from the Wilkinson Microwave Anisotropy Probe survey, using the Multifractal Detrended Fluctuation Analysis, Rescaled Range, and Scaled Windowed Variance methods. Multifractal Detrended Fluctuation Analysis shows that CMB fluctuations has a long-range correlation function with a multifractal behavior. By comparing the shuffled and surrogate series of CMB data, we conclude that the multifractality nature of the temperature fluctuation of CMB radiation is mainly due to the long-range correlations, and the map is consistent with a gaussian distribution.

  13. Coupled Quantum Fluctuations and Quantum Annealing

    Science.gov (United States)

    Hormozi, Layla; Kerman, Jamie

    We study the relative effectiveness of coupled quantum fluctuations, compared to single spin fluctuations, in the performance of quantum annealing. We focus on problem Hamiltonians resembling the the Sherrington-Kirkpatrick model of Ising spin glass and compare the effectiveness of different types of fluctuations by numerically calculating the relative success probabilities and residual energies in fully-connected spin systems. We find that for a small class of instances coupled fluctuations can provide improvement over single spin fluctuations and analyze the properties of the corresponding class. Disclaimer: This research was funded by ODNI, IARPA via MIT Lincoln Laboratory under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

  14. Stability and fluctuations in black hole thermodynamics

    International Nuclear Information System (INIS)

    Ruppeiner, George

    2007-01-01

    I examine thermodynamic fluctuations for a Kerr-Newman black hole in an extensive, infinite environment. This problem is not strictly solvable because full equilibrium with such an environment cannot be achieved by any black hole with mass M, angular momentum J, and charge Q. However, if we consider one (or two) of M, J, or Q to vary so slowly compared with the others that we can regard it as fixed, instances of stability occur, and thermodynamic fluctuation theory could plausibly apply. I examine seven cases with one, two, or three independent fluctuating variables. No knowledge about the thermodynamic behavior of the environment is needed. The thermodynamics of the black hole is sufficient. Let the fluctuation moment for a thermodynamic quantity X be √( 2 >). Fluctuations at fixed M are stable for all thermodynamic states, including that of a nonrotating and uncharged environment, corresponding to average values J=Q=0. Here, the fluctuation moments for J and Q take on maximum values. That for J is proportional to M. For the Planck mass it is 0.3990(ℎ/2π). That for Q is 3.301e, independent of M. In all cases, fluctuation moments for M, J, and Q go to zero at the limit of the physical regime, where the temperature goes to zero. With M fluctuating there are no stable cases for average J=Q=0. But, there are transitions to stability marked by infinite fluctuations. For purely M fluctuations, this coincides with a curve which Davies identified as a phase transition

  15. RF current drive and plasma fluctuations

    International Nuclear Information System (INIS)

    Peysson, Yves; Decker, Joan; Morini, L; Coda, S

    2011-01-01

    The role played by electron density fluctuations near the plasma edge on rf current drive in tokamaks is assessed quantitatively. For this purpose, a general framework for incorporating density fluctuations in existing modelling tools has been developed. It is valid when rf power absorption takes place far from the fluctuating region of the plasma. The ray-tracing formalism is modified in order to take into account time-dependent perturbations of the density, while the Fokker–Planck solver remains unchanged. The evolution of the electron distribution function in time and space under the competing effects of collisions and quasilinear diffusion by rf waves is determined consistently with the time scale of fluctuations described as a statistical process. Using the ray-tracing code C3PO and the 3D linearized relativistic bounce-averaged Fokker–Planck solver LUKE, the effect of electron density fluctuations on the current driven by the lower hybrid (LH) and the electron cyclotron (EC) waves is estimated quantitatively. A thin fluctuating layer characterized by electron drift wave turbulence at the plasma edge is considered. The effect of fluctuations on the LH wave propagation is equivalent to a random scattering process with a broadening of the poloidal mode spectrum proportional to the level of the perturbation. However, in the multipass regime, the LH current density profile remains sensitive to the ray chaotic behaviour, which is not averaged by fluctuations. The effect of large amplitude fluctuations on the EC driven current is found to be similar to an anomalous radial transport of the fast electrons. The resulting lower current drive efficiency and broader current profile are in better agreement with experimental observations. Finally, applied to the ITER ELMy H-mode regime, the model predicts a significant broadening of the EC driven current density profile with the fluctuation level, which can make the stabilization of neoclassical tearing mode potentially

  16. Thermal fluctuation levels of magnetic and electric fields in unmagnetized plasma: The rigorous relativistic kinetic theory

    International Nuclear Information System (INIS)

    Yoon, P. H.; Schlickeiser, R.; Kolberg, U.

    2014-01-01

    Any fully ionized collisionless plasma with finite random particle velocities contains electric and magnetic field fluctuations. The fluctuations can be of three different types: weakly damped, weakly propagating, or aperiodic. The kinetics of these fluctuations in general unmagnetized plasmas, governed by the competition of spontaneous emission, absorption, and stimulated emission processes, is investigated, extending the well-known results for weakly damped fluctuations. The generalized Kirchhoff radiation law for both collective and noncollective fluctuations is derived, which in stationary plasmas provides the equilibrium energy densities of electromagnetic fluctuations by the ratio of the respective spontaneous emission coefficient and the true absorption coefficient. As an illustrative example, the equilibrium energy densities of aperiodic transverse collective electric and magnetic fluctuations in an isotropic thermal electron-proton plasmas of density n e are calculated as |δB|=√((δB) 2 )=2.8(n e m e c 2 ) 1/2 g 1/2 β e 7/4 and |δE|=√((δE) 2 )=3.2(n e m e c 2 ) 1/2 g 1/3 β e 2 , where g and β e denote the plasma parameter and the thermal electron velocity in units of the speed of light, respectively. For densities and temperatures of the reionized early intergalactic medium, |δB|=6·10 −18 G and |δE|=2·10 −16 G result

  17. Grasping the mechanisms of narratives' incoherence in schizophrenia: an analysis of the temporal structure of patients' life story.

    Science.gov (United States)

    Allé, M C; Gandolphe, M-C; Doba, K; Köber, C; Potheegadoo, J; Coutelle, R; Habermas, T; Nandrino, J-L; Danion, J-M; Berna, F

    2016-08-01

    Life narratives of patients with schizophrenia are characterized by impaired coherence so that the listener has often difficulties to grasp the life trajectory of the patients. In order to better understand what causes this reduced temporal coherence, we investigated the temporal structure of patients' life narratives through different temporal narrative elements (elaboration of beginnings and endings, local temporal indicators and temporal deviations from a linear order), across two complementary studies. Life narratives were collected by means of two different methods; a free recall in study 1 and a more structured protocol, aiming at reducing the cognitive task demands in study 2. All narratives from the two studies were analyzed using the same validated method. Both studies showed that global temporal coherence is significantly reduced in patients with schizophrenia (ps.02). This is mainly due to their stronger tendency to temporally deviate from a linear temporal order without marking the deviation as such. We also observed significant correlations in the patient groups between global temporal coherence and executive dysfunction (p=.008) or their higher tendency to temporally deviate from a linear temporal order in their life narratives (p<.001). These results shed light on narrative correlates of temporal narrative incoherence in schizophrenia and highlight the central role of executive dysfunction in this incoherence. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Photonic generation of FCC-compliant UWB pulses based on modified Gaussian quadruplet and incoherent wavelength-to-time conversion

    Science.gov (United States)

    Mu, Hongqian; Wang, Muguang; Tang, Yu; Zhang, Jing; Jian, Shuisheng

    2018-03-01

    A novel scheme for the generation of FCC-compliant UWB pulse is proposed based on modified Gaussian quadruplet and incoherent wavelength-to-time conversion. The modified Gaussian quadruplet is synthesized based on linear sum of a broad Gaussian pulse and two narrow Gaussian pulses with the same pulse-width and amplitude peak. Within specific parameter range, FCC-compliant UWB with spectral power efficiency of higher than 39.9% can be achieved. In order to realize the designed waveform, a UWB generator based on spectral shaping and incoherent wavelength-to-time mapping is proposed. The spectral shaper is composed of a Gaussian filter and a programmable filter. Single-mode fiber functions as both dispersion device and transmission medium. Balanced photodetection is employed to combine linearly the broad Gaussian pulse and two narrow Gaussian pulses, and at same time to suppress pulse pedestals that result in low-frequency components. The proposed UWB generator can be reconfigured for UWB doublet by operating the programmable filter as a single-band Gaussian filter. The feasibility of proposed UWB generator is demonstrated experimentally. Measured UWB pulses match well with simulation results. FCC-compliant quadruplet with 10-dB bandwidth of 6.88-GHz, fractional bandwidth of 106.8% and power efficiency of 51% is achieved.

  19. Measurements of incoherent light and background structure at exo-Earth detection levels in the High Contrast Imaging Testbed

    Science.gov (United States)

    Cady, Eric; Shaklan, Stuart

    2014-08-01

    A major component of the estimation and correction of starlight at very high contrasts is the creation of a dark hole: a region in the vicinity of the core of the stellar point spread function (PSF) where speckles in the PSF wings have been greatly attenuated, up to a factor of 1010 for the imaging of terrestrial exoplanets. At these very high contrasts, removing these speckles requires distinguishing between light from the stellar PSF scattered by instrument imperfections, which may be partially corrected across a broad band using deformable mirrors in the system, from light from other sources which generally may not. These other sources may be external or internal to the instrument (e.g. planets, exozodiacal light), but in either case, their distinguishing characteristic is their inability to interfere coherently with the PSF. In the following we discuss the estimation, structure, and expected origin of this incoherent" signal, primarily in the context of a series of experiments made with a linear band-limited mask in Jan-Mar 2013. We find that the incoherent" signal at moderate contrasts is largely estimation error of the coherent signal, while at very high contrasts it represents a true floor which is stable over week-timescales.

  20. An Improved InSAR Image Co-Registration Method for Pairs with Relatively Big Distortions or Large Incoherent Areas

    Directory of Open Access Journals (Sweden)

    Zhenwei Chen

    2016-09-01

    Full Text Available Co-registration is one of the most important steps in interferometric synthetic aperture radar (InSAR data processing. The standard offset-measurement method based on cross-correlating uniformly distributed patches takes no account of specific geometric transformation between images or characteristics of ground scatterers. Hence, it is inefficient and difficult to obtain satisfying co-registration results for image pairs with relatively big distortion or large incoherent areas. Given this, an improved co-registration strategy is proposed in this paper which takes both the geometric features and image content into consideration. Firstly, some geometric transformations including scale, flip, rotation, and shear between images were eliminated based on the geometrical information, and the initial co-registration polynomial was obtained. Then the registration points were automatically detected by integrating the signal-to-clutter-ratio (SCR thresholds and the amplitude information, and a further co-registration process was performed to refine the polynomial. Several comparison experiments were carried out using 2 TerraSAR-X data from the Hong Kong airport and 21 PALSAR data from the Donghai Bridge. Experiment results demonstrate that the proposed method brings accuracy and efficiency improvements for co-registration and processing abilities in the cases of big distortion between images or large incoherent areas in the images. For most co-registrations, the proposed method can enhance the reliability and applicability of co-registration and thus promote the automation to a higher level.

  1. An Improved InSAR Image Co-Registration Method for Pairs with Relatively Big Distortions or Large Incoherent Areas.

    Science.gov (United States)

    Chen, Zhenwei; Zhang, Lei; Zhang, Guo

    2016-09-17

    Co-registration is one of the most important steps in interferometric synthetic aperture radar (InSAR) data processing. The standard offset-measurement method based on cross-correlating uniformly distributed patches takes no account of specific geometric transformation between images or characteristics of ground scatterers. Hence, it is inefficient and difficult to obtain satisfying co-registration results for image pairs with relatively big distortion or large incoherent areas. Given this, an improved co-registration strategy is proposed in this paper which takes both the geometric features and image content into consideration. Firstly, some geometric transformations including scale, flip, rotation, and shear between images were eliminated based on the geometrical information, and the initial co-registration polynomial was obtained. Then the registration points were automatically detected by integrating the signal-to-clutter-ratio (SCR) thresholds and the amplitude information, and a further co-registration process was performed to refine the polynomial. Several comparison experiments were carried out using 2 TerraSAR-X data from the Hong Kong airport and 21 PALSAR data from the Donghai Bridge. Experiment results demonstrate that the proposed method brings accuracy and efficiency improvements for co-registration and processing abilities in the cases of big distortion between images or large incoherent areas in the images. For most co-registrations, the proposed method can enhance the reliability and applicability of co-registration and thus promote the automation to a higher level.

  2. On black hole horizon fluctuations

    International Nuclear Information System (INIS)

    Tuchin, K.L.

    1999-01-01

    A study of the high angular momentum particles 'atmosphere' near the Schwarzschild black hole horizon suggested that strong gravitational interactions occur at invariant distance of the order of 3 √M [2]. We present a generalization of this result to the Kerr-Newman black hole case. It is shown that the larger charge and angular momentum black hole bears, the larger invariant distance at which strong gravitational interactions occur becomes. This invariant distance is of order 3 √((r + 2 )/((r + - r - ))). This implies that the Planckian structure of the Hawking radiation of extreme black holes is completely broken

  3. Analysis of Numerical Simulation Database for Pressure Fluctuations Induced by High-Speed Turbulent Boundary Layers

    Science.gov (United States)

    Duan, Lian; Choudhari, Meelan M.

    2014-01-01

    Direct numerical simulations (DNS) of Mach 6 turbulent boundary layer with nominal freestream Mach number of 6 and Reynolds number of Re(sub T) approximately 460 are conducted at two wall temperatures (Tw/Tr = 0.25, 0.76) to investigate the generated pressure fluctuations and their dependence on wall temperature. Simulations indicate that the influence of wall temperature on pressure fluctuations is largely limited to the near-wall region, with the characteristics of wall-pressure fluctuations showing a strong temperature dependence. Wall temperature has little influence on the propagation speed of the freestream pressure signal. The freestream radiation intensity compares well between wall-temperature cases when normalized by the local wall shear; the propagation speed of the freestream pressure signal and the orientation of the radiation wave front show little dependence on the wall temperature.

  4. Interplay between total thickness and period thickness in the phonon thermal conductivity of superlattices from the nanoscale to the microscale: Coherent versus incoherent phonon transport

    Science.gov (United States)

    Cheaito, Ramez; Polanco, Carlos A.; Addamane, Sadhvikas; Zhang, Jingjie; Ghosh, Avik W.; Balakrishnan, Ganesh; Hopkins, Patrick E.

    2018-02-01

    We report on the room temperature thermal conductivity of AlAs-GaAs superlattices (SLs), in which we systematically vary the period thickness and total thickness between 2 -24 nm and 20.1 -2 ,160 nm , respectively. The thermal conductivity increases with the SL thickness and plateaus at a thickness around 200 nm, showing a clear transition from a quasiballistic to a diffusive phonon transport regime. These results demonstrate the existence of classical size effects in SLs, even at the highest interface density samples. We use harmonic atomistic Green's function calculations to capture incoherence in phonon transport by averaging the calculated transmission over several purely coherent simulations of independent SL with different random mixing at the AlAs-GaAs interfaces. These simulations demonstrate the significant contribution of incoherent phonon transport through the decrease in the transmission and conductance in the SLs as the number of interfaces increases. In spite of this conductance decrease, our simulations show a quasilinear increase in thermal conductivity with the superlattice thickness. This suggests that the observation of a quasilinear increase in thermal conductivity can have important contributions from incoherent phonon transport. Furthermore, this seemingly linear slope in thermal conductivity versus SL thickness data may actually be nonlinear when extended to a larger number of periods, which is a signature of incoherent effects. Indeed, this trend for superlattices with interatomic mixing at the interfaces could easily be interpreted as linear when the number of periods is small. Our results reveal that the change in thermal conductivity with period thickness is dominated by incoherent (particlelike) phonons, whose properties are not dictated by changes in the AlAs or GaAs phonon dispersion relations. This work demonstrates the importance of studying both period and sample thickness dependencies of thermal conductivity to understand the

  5. Spontaneous Radiation Background Calculation for LCLS

    CERN Document Server

    Reiche, Sven

    2004-01-01

    The intensity of undulator radiation, not amplified by the FEL interaction, can be larger than the maximum FEL signal in the case of an X-ray FEL. In the commissioning of a SASE FEL it is essential to extract an amplified signal early to diagnose eventual misalignment of undulator modules or errors in the undulator field strength. We developed a numerical code to calculate the radiation pattern at any position behind a multi-segmented undulator with arbitrary spacing and field profiles. The output can be run through numerical spatial and frequency filters to model the radiation beam transport and diagnostic. In this presentation we estimate the expected background signal for the FEL diagnostic and at what point along the undulator the FEL signal can be separated from the background. We also discusses how much information on the undulator field and alignment can be obtained from the incoherent radiation signal itself.

  6. Fluctuating Asymmetry of Human Populations: A Review

    Directory of Open Access Journals (Sweden)

    John H. Graham

    2016-12-01

    Full Text Available Fluctuating asymmetry, the random deviation from perfect symmetry, is a widely used population-level index of developmental instability, developmental noise, and robustness. It reflects a population’s state of adaptation and genomic coadaptation. Here, we review the literature on fluctuating asymmetry of human populations. The most widely used bilateral traits include skeletal, dental, and facial dimensions; dermatoglyphic patterns and ridge counts; and facial shape. Each trait has its advantages and disadvantages, but results are most robust when multiple traits are combined into a composite index of fluctuating asymmetry (CFA. Both environmental (diet, climate, toxins and genetic (aneuploidy, heterozygosity, inbreeding stressors have been linked to population-level variation in fluctuating asymmetry. In general, these stressors increase average fluctuating asymmetry. Nevertheless, there have been many conflicting results, in part because (1 fluctuating asymmetry is a weak signal in a sea of noise; and (2 studies of human fluctuating asymmetry have not always followed best practices. The most serious concerns are insensitive asymmetry indices (correlation coefficient and coefficient of indetermination, inappropriate size scaling, unrecognized mixture distributions, inappropriate corrections for directional asymmetry, failure to use composite indices, and inattention to measurement error. Consequently, it is often difficult (or impossible to compare results across traits, and across studies.

  7. Effects of density gradients and fluctuations at the plasma edge on ECEI measurements at ASDEX Upgrade

    NARCIS (Netherlands)

    Vanovac, B.; Wolfrum, E.; Denk, S. S.; Mink, F.; Laggner, F. M.; Birkenmeier, G.; Willensdorfer, M.; Viezzer, E.; Hoelzl, M.; Freethy, S. J.; Dunne, M. G.; Lessig, A.; Luhmann, N. C.; ASDEX Upgrade team,; EUROfusion MST1 Team,

    2018-01-01

    Electron cyclotron emission imaging (ECEI) provides measurements of electron temperature (T-e) and its fluctuations (delta T-e). However, when measuring at the plasma edge, in the steep gradient region, radiation transport effects must be taken into account. It is shown that due to these effects,

  8. Analysis of fluctuations in semiconductor devices

    Science.gov (United States)

    Andrei, Petru

    The random nature of ion implantation and diffusion processes as well as inevitable tolerances in fabrication result in random fluctuations of doping concentrations and oxide thickness in semiconductor devices. These fluctuations are especially pronounced in ultrasmall (nanoscale) semiconductor devices when the spatial scale of doping and oxide thickness variations become comparable with the geometric dimensions of devices. In the dissertation, the effects of these fluctuations on device characteristics are analyzed by using a new technique for the analysis of random doping and oxide thickness induced fluctuations. This technique is universal in nature in the sense that it is applicable to any transport model (drift-diffusion, semiclassical transport, quantum transport etc.) and it can be naturally extended to take into account random fluctuations of the oxide (trapped) charges and channel length. The technique is based on linearization of the transport equations with respect to the fluctuating quantities. It is computationally much (a few orders of magnitude) more efficient than the traditional Monte-Carlo approach and it yields information on the sensitivity of fluctuations of parameters of interest (e.g. threshold voltage, small-signal parameters, cut-off frequencies, etc.) to the locations of doping and oxide thickness fluctuations. For this reason, it can be very instrumental in the design of fluctuation-resistant structures of semiconductor devices. Quantum mechanical effects are taken into account by using the density-gradient model as well as through self-consistent Poisson-Schrodinger computations. Special attention is paid to the presenting of the technique in a form that is suitable for implementation on commercial device simulators. The numerical implementation of the technique is discussed in detail and numerous computational results are presented and compared with those previously published in literature.

  9. Computer simulations of phospholipid - membrane thermodynamic fluctuations

    DEFF Research Database (Denmark)

    Pedersen, U.R.; Peters, Günther H.j.; Schröder, T.B.

    2008-01-01

    This paper reports all-atom computer simulations of five phospholipid membranes, DMPC, DPPC, DMPG, DMPS, and DMPSH, with a focus on the thermal equilibrium fluctuations of volume, energy, area, thickness, and order parameter. For the slow fluctuations at constant temperature and pressure (defined...... membranes, showing a similar picture. The cause of the observed strong correlations is identified by splitting volume and energy into contributions from tails, heads, and water, showing that the slow volume-energy fluctuations derive from the tail region’s van der Waals interactions and are thus analogous...

  10. Charge-imbalance fluctuations in superconductors

    International Nuclear Information System (INIS)

    Lemberger, T.R.

    1981-01-01

    We calculate that the mean-square amplitude of the fluctuations of the condensate chemical potential μ/sub s/ due to charge-imbalance fluctuations in the limit Δ/k/sub B/T 2 > = 2(k/sub B/T) 2 /πdeltaΩN(0) in a volume Ω of superconductor. We relate these fluctuations via Nyquist's theorem to measured values of the contribution of self-injected charge imbalance to the dc resistance of SIN tunnel junctions. In this relation the dynamic charge-imbalance relaxation rate is 1/tau/sub E/, the electron-phonon scattering rate

  11. Fluctuations and transport in an inhomogeneous plasma

    International Nuclear Information System (INIS)

    Nevins, W.M.; Chen, L.

    1979-11-01

    A formalism is developed for calculating the equilibrium fluctuation level in an inhomogeneous plasma. This formalism is applied to the collisionless drift wave in a sheared magnetic field. The fluctuation level is found to be anomalously large due to both the presence of weakly damped normal modes and convective amplification. As the magnetic shear is reduced, the steady-state fluctuation spectrum is found to increase both in coherence and in amplitude. The transport associated with this mode is evaluated. The diffusion coefficient is found to scale as D is proportional to B 2 /nT/sup 1/2/

  12. Pairing fluctuations in trapped Fermi gases

    International Nuclear Information System (INIS)

    Viverit, Luciano; Bruun, Georg M.; Minguzzi, Anna; Fazio, Rosario

    2004-01-01

    We examine the contribution of pairing fluctuations to the superfluid order parameter for harmonically trapped atomic Fermi gases in the BCS regime. In the limit of small systems we consider, both analytically and numerically, their space and temperature dependence. We predict a parity effect, i.e., that pairing fluctuations show a maximum or a minimum at the center of the trap, depending on the value of the last occupied shell being even or odd. We propose to detect pairing fluctuations by measuring the density-density correlation function after a ballistic expansion of the gas

  13. Enhanced ion acoustic fluctuations and ion outflows

    Directory of Open Access Journals (Sweden)

    F. R. E. Forme

    1999-02-01

    Full Text Available A number of observations showing enhanced ion acoustic echoes observed by means of incoherent scatter radars have been reported in the literature. The received power is extremely enhanced by up to 1 or 2 orders of magnitude above usual values, and it is mostly contained in one of the two ion acoustic lines. This spectral asymmetry and the intensity of the received signal cannot be resolved by the standard analysis procedure and often causes its failure. As a result, and in spite of a very clear spectral signature, the analysis is unable to fit the plasma parameters inside the regions of ion acoustic turbulence. We present European Incoherent Scatter radar (EISCAT observations of large ion outflows associated with the simultaneous occurrence of enhanced ion acoustic echoes. The ion fluxes can reach 1014 m-2 s-1 at 800 km altitude. From the very clear spectral signatures of these echoes, a method is presented to extract estimates of the electron temperature and the ion drift within the turbulent regions. It is shown that the electron gas is strongly heated up to 11 000 K. Also electron temperature gradients of about 0.02 K/m exist. Finally, the estimates of the electron temperature and of the ion drift are used to study the possible implications for the plasma transport inside turbulent regions. It is shown that strong electron temperature gradients cause enhancement of the ambipolar electric field and can account for the observed ion outflows.Key words. Ionosphere (auroral ionosphere; ionosphere · magnetosphere interactions; plasma waves and instabilities.

  14. Proof of the Feasibility of Coherent and Incoherent Schemes for Pumping a Gamma-Ray Laser

    Science.gov (United States)

    1993-08-31

    Eq. (1) as functions of the It was the purpose of the work reported here to exam . end-point energies of the irradiating spectra showed very ine the...34 lTam isomeric populations into freely radiating states. Reported values (Collins et al. 1990) are summarized in table I ard shown schematically in figure

  15. Plasma diffusion due to magnetic field fluctuations

    International Nuclear Information System (INIS)

    Okuda, H.; Lee, W.W.; Lin, A.T.

    1979-01-01

    Plasma diffusion due to magnetic field fluctuations has been studied in two dimensions for a plasma near thermal equilibrium and when the fluctuations are suprathermal. It is found that near thermal equilibrium electron diffusion varies as B -2 when the collisionless skin depth is greater than the thermal electron gyroradius and is generally smaller than the diffusion due to collisions or electrostatic fluctuations for a low-β plasma. When the suprathermal magnetic fluctuation exists because of macroscopic plasma currents, electron diffusion is enhanced due to the coalescence of current filaments and magnetic islands. Magnetic field energy is found to condense to the longest wavelength available in the system and stays there longer than the electron diffusion time scale

  16. Magnetic fluctuations and heavy electron superconductivity

    International Nuclear Information System (INIS)

    Norman, M.R.

    1988-01-01

    A magnetic fluctuation self-energy based on neutron scattering data is used to calculate mass renormalizations, and superconducting critical temperatures and order parameters, for various heavy electron metals

  17. Metric fluctuations and their evolution during inflation

    International Nuclear Information System (INIS)

    Anabitarte, M.; Bellini, M.

    2004-01-01

    We discuss the evolution of the fluctuations in a symmetric φ c -exponential potential which provides a power-law expansion during inflation using both the gauge-invariant field Φ and the Sasaki-Mukhanov field. (orig.)

  18. Novikov Engine with Fluctuating Heat Bath Temperature

    Science.gov (United States)

    Schwalbe, Karsten; Hoffmann, Karl Heinz

    2018-04-01

    The Novikov engine is a model for heat engines that takes the irreversible character of heat fluxes into account. Using this model, the maximum power output as well as the corresponding efficiency of the heat engine can be deduced, leading to the well-known Curzon-Ahlborn efficiency. The classical model assumes constant heat bath temperatures, which is not a reasonable assumption in the case of fluctuating heat sources. Therefore, in this article the influence of stochastic fluctuations of the hot heat bath's temperature on the optimal performance measures is investigated. For this purpose, a Novikov engine with fluctuating heat bath temperature is considered. Doing so, a generalization of the Curzon-Ahlborn efficiency is found. The results can help to quantify how the distribution of fluctuating quantities affects the performance measures of power plants.

  19. Total charge fluctuation in heavy ion collision

    International Nuclear Information System (INIS)

    Mishra, D.K.; Netrakanti, P.K.; Mohanty, A.K.; Garg, P.

    2014-01-01

    Event-by-event fluctuations of positive, negative, total and net charge produced in relativistic nuclear collisions have been of interest to explore phase transition and/or a critical end point (CEP) which is believed to exist somewhere between the hadronic phase and the quark-gluon phase of the QCD phase diagram. The entropy is closely related to the particle multiplicity, and it is expected to be approximately conserved during the evolution of the matter created at the early stage. The entropy fluctuations are not directly observed but can be inferred from the experimentally measured quantities. The final state mean multiplicity is proportional to the entropy of the initial state ( ∼ S). The particle multiplicity can be measured on an event-by-event basis, whereas the entropy is defined by averaging the particle multiplicities in the ensemble of events. Thus, the dynamical entropy fluctuations can be measured experimentally by measuring the fluctuations in the mean multiplicity

  20. Fluctuations, dynamical instabilities and clusterization processes

    International Nuclear Information System (INIS)

    Burgio, G.F.; Chomaz, Ph.; Randrup, J.

    1992-01-01

    Recent progress with regard to the numerical simulation of fluctuations in nuclear dynamics is reported. Cluster formation in unstable nuclear matter is studied within the framework of a Boltzmann-Langevin equation developed to describe large amplitude fluctuations. Through the Fourier analysis of the fluctuating nuclear density in coordinate space, the onset of the clusterization is related to the dispersion relation of harmonic density oscillations. This detailed study on the simple two-dimensional case demonstrates the validity of the general approach. It is also shown, how the inclusion of fluctuations implies a description in terms of ensemble of trajectories and it is discussed why the presence of a stochastic term may cure the intrinsic unpredictability of deterministic theories (such as mean-field approximation) in presence of instabilities and/or chaos. (author) 8 refs., 3 figs

  1. Collective fluctuations in networks of noisy components

    International Nuclear Information System (INIS)

    Masuda, Naoki; Kawamura, Yoji; Kori, Hiroshi

    2010-01-01

    Collective dynamics result from interactions among noisy dynamical components. Examples include heartbeats, circadian rhythms and various pattern formations. Because of noise in each component, collective dynamics inevitably involve fluctuations, which may crucially affect the functioning of the system. However, the relation between the fluctuations in isolated individual components and those in collective dynamics is not clear. Here, we study a linear dynamical system of networked components subjected to independent Gaussian noise and analytically show that the connectivity of networks determines the intensity of fluctuations in the collective dynamics. Remarkably, in general directed networks including scale-free networks, the fluctuations decrease more slowly with system size than the standard law stated by the central limit theorem. They even remain finite for a large system size when global directionality of the network exists. Moreover, such non-trivial behavior appears even in undirected networks when nonlinear dynamical systems are considered. We demonstrate it with a coupled oscillator system.

  2. Edge fluctuation studies in Heliotron J

    International Nuclear Information System (INIS)

    Mizuuchi, T.; Chechkin, V.V.; Ohashi, K.; Sorokovoy, E.L.; Chechkin, A.V.; Gonchar, V.Yu.; Takahashi, K.; Kobayashi, S.; Nagasaki, K.; Okada, H.; Yamamoto, S.; Sano, F.; Kondo, K.; Nishino, N.; Kawazome, H.; Shidara, H.; Kaneko, S.; Fukagawa, Y.; Morita, Y.; Nakazawa, S.; Nishio, S.; Tsuboi, S.; Yamada, M.

    2005-01-01

    Low frequency and small-scale fluctuations of density and potential near the last closed flux surface are investigated by using Langmuir probes for the second harmonic ECH plasmas in a helical-axis heliotron device, Heliotron J. The existence of a plasma layer with a radial electric field shear was indicated near the last closed flux surface. Near this layer, the reversal of phase velocity and de-correlation of the fluctuations were observed. On the other hand, it is suggested that a considerable fraction of the fluctuation induced particle flux is carried off through the intermittent events. Preliminary analyses to classify the PDFs of the ion-saturation current fluctuation as stable Levy distributions demonstrate that the Levy index decreases from the inner to the outer region of edge plasma, suggesting that the PDFs near the boundary region of Heliotron J are nearly Gaussian, whereas at the outer regions of plasma they become strongly non-Gaussian

  3. Fluctuation conductivity of thin superconductive vanadium films

    International Nuclear Information System (INIS)

    Dmitrenko, I.M.; Sidorenko, A.S.; Fogel, N.Y.

    1982-01-01

    Resistive transitions into the superconductive state are studied in thin [d >T/sub c/ the experimental data on the excess conductivity of the films agree qualitatively and quantitively with Aslamazov--Larkin theory. There is no Maki--Thompson contribution to fluctuation conductivity. Near T/sub c/ the excess conductivity sigma' changes exponentially with temperature in accordance with the predictions of the theory of the critical fluctuations of the order parameter. The values of the effective charge carrier mass defined from data on sigma' for the low fluctuation and critical fluctuation regions differ markedly. This difference is within the spread of effective masses for various charge carrier groups already known for vanadium. Causes of the difference in resistive behavior for the regions T >T/sub c/ are considered

  4. Fluctuations at electrode-YSZ interfaces

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Hansen, Karin Vels; Skou, Eivind

    2005-01-01

    Current fluctuations at potentiostatically controlled point electrodes of Pt, La$_{0.85}$Sr$_{0.15}$MnO$_3$ and Ni on YSZ surfaces are determined at 1000$^\\circ$C. For the oxygen reduction process on Pt electrodes characteristic sawtooth shaped low frequency fluctuations are observed. At temperat......Current fluctuations at potentiostatically controlled point electrodes of Pt, La$_{0.85}$Sr$_{0.15}$MnO$_3$ and Ni on YSZ surfaces are determined at 1000$^\\circ$C. For the oxygen reduction process on Pt electrodes characteristic sawtooth shaped low frequency fluctuations are observed....../water atmosphere are presented for discussion. The origin of the observations is not known at present but it appears likely that they are related to the activation/deactivation mechanism of SOFCs....

  5. Temperature fluctuations in the Atlantic Ocean

    International Nuclear Information System (INIS)

    Hjoello, Solfrid Saetre

    2005-01-01

    The article discusses the temperature fluctuations in connection with drought in Africa, the climate in North America, the European heat waves and the frequent tropical hurricanes in the Atlantic Ocean. Problems with climate modelling and some pollution aspects are mentioned

  6. Ultraviolet germicidal efficacy as a function of pulsed radiation parameters studied by spore film dosimetry.

    Science.gov (United States)

    Bauer, Stefan; Holtschmidt, Hans; Ott, Günter

    2018-01-01

    Disinfection by pulsed ultraviolet (UV) radiation is a commonly used method, e.g. in industry or medicine and can be carried out either with lasers or broadband UV radiation sources. Detrimental effects to biological materials depending on parameters such as pulse duration τ or pulse repetition frequency f p are well-understood for pulsed coherent UV radiation, however, relatively little is known for its incoherent variant. Therefore, within this work, it is the first time that disinfection rates of pulsed and continuous (cw) incoherent UV radiation studied by means of spore film dosimetry are presented, compared with each other, and in a second step further investigated regarding two pulse parameters. After analyzing the dynamic range of the Bacillus subtilis spore films with variable cw radiant exposures H=5-100Jm -2 a validation of the Bunsen-Roscoe law revealed its restricted applicability and a 28% enhanced detrimental effect of pulsed compared to cw incoherent UV radiation. A radiant exposure H=50Jm -2 and an irradiance E=0.5Wm -2 were found to be suitable parameters for an analysis of the disinfection rate as a function of τ=0.5-10ms and f p =25-500Hz unveiling that shorter pulses and lower frequencies inactivate more spores. Finally, the number of applied pulses as well as the experiment time were considered with regard to spore film disinfection. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Density Fluctuations in a Polar Coronal Hole

    Science.gov (United States)

    Hahn, Michael; D’Huys, Elke; Savin, Daniel Wolf

    2018-06-01

    We have measured the root-mean-square (rms) amplitude of intensity fluctuations, ΔI, in plume and interplume regions of a polar coronal hole. These intensity fluctuations correspond to density fluctuations. Using data from the Sun Watcher using the Active Pixel System detector and Image Processing on the Project for Onboard Autonomy (Proba2), our results extend up to a height of about 1.35 R ⊙. One advantage of the rms analysis is that it does not rely on a detailed evaluation of the power spectrum, which is limited by noise levels to low heights in the corona. The rms approach can be performed up to larger heights where the noise level is greater, provided that the noise itself can be quantified. At low heights, both the absolute ΔI, and the amplitude relative to the mean intensity, ΔI/I, decrease with height. However, starting at about 1.2 R ⊙, ΔI/I increases, reaching 20%–40% by 1.35 R ⊙. This corresponds to density fluctuations of Δn e/n e ≈ 10%–20%. The increasing relative amplitude implies that the density fluctuations are generated in the corona itself. One possibility is that the density fluctuations are generated by an instability of Alfvén waves. This generation mechanism is consistent with some theoretical models and with observations of Alfvén wave amplitudes in coronal holes. Although we find that the energy of the observed density fluctuations is small, these fluctuations are likely to play an important indirect role in coronal heating by promoting the reflection of Alfvén waves and driving turbulence.

  8. Density fluctuations in ohmic Asdex discharges

    International Nuclear Information System (INIS)

    Dodel, G.; Holzhauer, E.

    1989-01-01

    The investigations on the wave-number and frequency spectra of the density fluctuations, occurring in the different operational modes of ASDEX, are summarized. The aim of the experiments is to study the physical nature of fluctuations and their influence on anomalous transport. The scattering system is described. The results reported were obtained using a 100 mW, λ = 119 μm CW CH-30H laser and homodyne detection

  9. Fluorescence fluctuation spectroscopy (FFS), part A

    CERN Document Server

    Tetin, Sergey

    2013-01-01

    This new volume of Methods in Enzymology continues the legacy of this premier serial by containing quality chapters authored by leaders in the field. This volume covers Fluorescence Fluctuation SpectroscopyContains chapters on such topics as Time-integrated fluorescence cumulant analysis, Pulsed Interleaved Excitation, and raster image correlation spectroscopy and number and brightness analysis.Continues the legacy of this premier serial with quality chapters authored by leaders in the fieldCovers fluorescence fluctuation spectroscopyContains chapte

  10. Addendum to ''Density fluctuations in liquid rubidium''

    International Nuclear Information System (INIS)

    Haan, S.W.; Mountain, R.D.; Hsu, C.S.; Rahman, A.

    1980-01-01

    We performed molecular-dynamics simulations of liquid rubidium and the Lennard-Jones fluid at several densities and temperatures, and of a system whose pair potential is the repulsive core of the rubidium potential. In all cases, propagating density fluctuations occurred in the rubidiumlike systems at much shorter wavelengths than in the Lennard-Jones system. This indicates that the repulsive part of the pair potential is the dominant factor in determining the relaxation of short-wavelength density fluctuations

  11. Current fluctuations of interacting active Brownian particles

    OpenAIRE

    Pre, Trevor Grand; Limmer, David T.

    2018-01-01

    We derive the distribution function for particle currents for a system of interacting active Brownian particles in the long time limit using large deviation theory and a weighted many body expansion. We find the distribution is non-Gaussian, except in the limit of passive particles. The non-Gaussian fluctuations can be understood from the effective potential the particles experience when conditioned on a given current. This potential suppresses fluctuations of the particle's orientation, and ...

  12. Non-equilibrium fluctuation-induced interactions

    International Nuclear Information System (INIS)

    Dean, David S

    2012-01-01

    We discuss non-equilibrium aspects of fluctuation-induced interactions. While the equilibrium behavior of such interactions has been extensively studied and is relatively well understood, the study of these interactions out of equilibrium is relatively new. We discuss recent results on the non-equilibrium behavior of systems whose dynamics is of the dissipative stochastic type and identify a number of outstanding problems concerning non-equilibrium fluctuation-induced interactions.

  13. Magnetic fluctuations can contribute to plasma transport, ''self-consistency constraints'' notwithstanding

    International Nuclear Information System (INIS)

    Krommes, J.A.; Kim, Chang-Bae.

    1987-09-01

    The recent conclusion that in a turbulent, collisionless plasma ''magnetic transport including quasilinear magnetic flutter transport ... does not contribute to the relaxation of (f), and thus is not responsible for electron energy or momentum transport'' is shown to be incorrect for a variety of situations of physical interest, including saturation by quasilinear plateau formation, induced scattering, and, most importantly, conventional mode coupling. The well-established theory of the mean infinitesimal response function and the spectral balance equation provides a unifying framework for understanding the above conclusion. In particular, the cancellations which lead to their conclusion are special cases of well-known relationships between the response function, particle propagator, and dielectric function. A more general, concise, and manifestly gauge-invariant algebraic derivation of the cancellations is given. Though the cancellations occur in a certain limit, these conclusions do not follow in general: The picture of steady-state turbulence as consisting of small-scale ''incoherent'' ballistic ''clumps'' shielded by long-wavelength ''coherent'' dielectric response is physically misleading and mathematically incomplete, as it ignores or mistreates the often dominant process of renormalized n-wave coupling. Thus, when ion nonlinearities are considered, formulas for the magnetic contribution to transport emerge which are quite similar to the quasilinear one. Furthermore, limits are possible in which all or part of the noise can be negligible, yet in which the total fluctuation spectrum remains finite. 56 refs

  14. Longitudinal fluctuations and decorrelation of anisotropic flow

    Energy Technology Data Exchange (ETDEWEB)

    Pang, Long-Gang [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main (Germany); Petersen, Hannah [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main (Germany); Institute for Theoretical Physics, Goethe University, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main (Germany); GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany); Qin, Guang-You [Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 430079 (China); Roy, Victor [Institute for Theoretical Physics, Goethe University, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main (Germany); Wang, Xin-Nian [Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 430079 (China); Nuclear Science Division MS70R0319, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2016-12-15

    We investigate the decorrelation of 2nd and 3rd order anisotropic flow for charged particles in two different pseudo rapidity (η) windows by varying the pseudo rapidity gap, in an event-by-event (3+1)D ideal hydrodynamic model, with fluctuating initial conditions from A Multi-Phase Transport (AMPT) model. We visualize the parton distribution at initial state for Pb+Pb collisions at LHC and Au+Au collisions at RHIC, and demonstrate the longitudinal fluctuations originating from the asymmetry between forward and backward going participants, the fluctuations of the string length and the fluctuations due to finite number of partons at different beam energies. The decorrelation of anisotropic flow of final hadrons with large η gaps is found to originate from the spatial decorrelation along the longitudinal direction in the AMPT initial conditions through hydrodynamic evolution. The agreement between our results and recent CMS data in most centralities suggests that the string-like mechanism of initial parton production in AMPT model captures the initial longitudinal fluctuation that is responsible for the measured decorrelation of anisotropic flow in Pb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest RHIC energy show stronger longitudinal decorrelation than at LHC, indicating larger longitudinal fluctuations at lower beam energies.

  15. Origin of density fluctuations in extended inflation

    International Nuclear Information System (INIS)

    Kolb, E.W.; Salopek, D.S.; Turner, M.S.

    1990-01-01

    We calculate both the curvature and isocurvature density fluctuations that arise due to quantum fluctuations in a simple model of extended inflation based upon the Jordan-Brans-Dicke theory. The curvature fluctuations that arise due to quantum fluctuations in the Brans-Dicke field in general have a non-scale-invariant spectrum and an amplitude that is cosmologically acceptable and interesting without having to tune any coupling constant to a very small value. The curvature perturbations that arise due to the Higgs field are subdominant. If there are other massless fields in the theory, e.g., an axion or an ilion, then isocurvature fluctuations arise in these fields too. Production of gravitational waves and the massless particles associated with excitations of the Brans-Dicke field are also discussed. Several attempts at more realistic models of extended inflation are also analyzed. The importance of the Einstein conformal frame in calculating curvature fluctuations is emphasized. When viewed in this frame, extended inflation closely resembles slow-rollover inflation with an exponential potential, and the usual formula for the amplitude of curvature perturbations applies directly

  16. Origin of density fluctuations in extended inflation

    International Nuclear Information System (INIS)

    Kolb, E.W.; Salopek, D.S.; Turner, M.S.

    1990-05-01

    The density fluctuations (both curvature and isocurvature) that arise due to quantum fluctuations in a simple model of extended inflation based upon the Jordan-Brans-Dicke theory are calculated. Curvature fluctuations arise due to quantum fluctuations in the Brans-Dicke field, in general have a nonscale-invariant spectrum, and can have an amplitude that is cosmologically acceptable and interesting without having to tune any coupling constant to a very small value. The density perturbations that arise due to the inflation field are subdominant. If there are other massless fields in the theory, e.g., an axion or an ilion, then isocurvature fluctuations arise in these fields too. Production of gravitational waves and the massless particles associated with excitations of the Brans-Dicke field are also discussed. Several attempts at more realistic models of extended inflation are also analyzed. The importance of the Einstein conformal frame in calculating curvature fluctuations is emphasized. When viewed in this frame, extended inflation closely resembles slow-rollover inflation with an exponential potential and the usual formula for the amplitude of curvature perturbations applies

  17. Influence of thermal fluctuations on ligament break-up: a fluctuating lattice Boltzmann study

    Science.gov (United States)

    Xue, Xiao; Biferale, Luca; Sbragaglia, Mauro; Toschi, Federico

    2017-11-01

    Thermal fluctuations are essential ingredients in a nanoscale system, driving Brownian motion of particles and capillary waves at non-ideal interfaces. Here we study the influence of thermal fluctuations on the breakup of liquid ligaments at the nanoscale. We offer quantitative characterization of the effects of thermal fluctuations on the Plateau-Rayleigh mechanism that drives the breakup process of ligaments. Due to thermal fluctuations, the droplet sizes after break-up need to be analyzed in terms of their distribution over an ensemble made of repeated experiments. To this aim, we make use of numerical simulations based on the fluctuating lattice Boltzmann method (FLBM) for multicomponent mixtures. The method allows an accurate and efficient simulation of the fluctuating hydrodynamics equations of a binary mixture, where both stochastic viscous stresses and diffusion fluxes are introduced. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No 642069.

  18. Influence of beam divergence on form-factor in X-ray diffraction radiation

    International Nuclear Information System (INIS)

    Sergeeva, D.Yu.; Tishchenko, A.A.; Strikhanov, M.N.

    2015-01-01

    Diffraction radiation from divergent beam is considered in terms of radiation in UV and X-ray range. Scedastic form of Gaussian distribution of the particle in the bunch, i.e. Gaussian distribution with changing dispersion has been used, which is more adequate for description of divergent beams than often used Gaussian distribution with constant dispersion. Both coherent and incoherent form-factors are taken into account. The conical diffraction effect in diffraction radiation is proved to make essential contribution in spectral-angular characteristics of radiation from a divergent beam

  19. Fluctuation dynamics in geoelectrical data: an investigation by using multifractal detrended fluctuation analysis

    International Nuclear Information System (INIS)

    Telesca, Luciano; Colangelo, Gerardo; Lapenna, Vincenzo; Macchiato, Maria

    2004-01-01

    We analyzed fluctuations in the time dynamics of nonstationary geoelectrical data, recorded in a seismic area of southern Italy, by means of the multifractal detrended fluctuation analysis (MF-DFA). The multifractal character of the signal depends mostly on the different long-range properties for small and large fluctuations. The time variation of indices, denoting the departure from monofractal behaviour, reveals an enhancement of the multifractality of the signal prior seismic occurrences

  20. Multi-stage En/decoders integrated in low loss Si3N4-SiO2 for incoherent spectral amplitude OCDMA on PON

    NARCIS (Netherlands)

    Huiszoon, B.; Leinse, Arne; Geuzebroek, D.H.; Augustin, L.M.; Klein, E.J.; de Waardt, H.; Khoe, G.D.; Koonen, A.M.J.; Emplit, Ph.; Delqué, M.; Gorza, S.-P.; Kockaert, P.; Leijtens, X

    2007-01-01

    In this paper, we show and analyze, for the first time, the static performance of integrated multi-stage cascade and tree spectral amplitude OCDMA en/decoders (E/Ds) which are fabricated in the low loss Si3N4–SiO2 material system. Combined with incoherent broad spectral sources these E/Ds enable

  1. Plasma wakefields driven by an incoherent combination of laser pulses: a path towards high-average power laser-plasma accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Benedetti, C.; Schroeder, C.B.; Esarey, E.; Leemans, W.P.

    2014-05-01

    he wakefield generated in a plasma by incoherently combining a large number of low energy laser pulses (i.e.,without constraining the pulse phases) is studied analytically and by means of fully-self-consistent particle-in-cell simulations. The structure of the wakefield has been characterized and its amplitude compared with the amplitude of the wake generated by a single (coherent) laser pulse. We show that, in spite of the incoherent nature of the wakefield within the volume occupied by the laser pulses, behind this region the structure of the wakefield can be regular with an amplitude comparable or equal to that obtained from a single pulse with the same energy. Wake generation requires that the incoherent structure in the laser energy density produced by the combined pulses exists on a time scale short compared to the plasma period. Incoherent combination of multiple laser pulses may enable a technologically simpler path to high-repetition rate, high-average power laser-plasma accelerators and associated applications.

  2. Influence of incoherent twin boundaries on the electrical properties of β-Ga2O3 layers homoepitaxially grown by metal-organic vapor phase epitaxy

    Science.gov (United States)

    Fiedler, A.; Schewski, R.; Baldini, M.; Galazka, Z.; Wagner, G.; Albrecht, M.; Irmscher, K.

    2017-10-01

    We present a quantitative model that addresses the influence of incoherent twin boundaries on the electrical properties in β-Ga2O3. This model can explain the mobility collapse below a threshold electron concentration of 1 × 1018 cm-3 as well as partly the low doping efficiency in β-Ga2O3 layers grown homoepitaxially by metal-organic vapor phase epitaxy on (100) substrates of only slight off-orientation. A structural analysis by transmission electron microscopy (TEM) reveals a high density of twin lamellae in these layers. In contrast to the coherent twin boundaries parallel to the (100) plane, the lateral incoherent twin boundaries exhibit one dangling bond per unit cell that acts as an acceptor-like electron trap. Since the twin lamellae are thin, we consider the incoherent twin boundaries to be line defects with a density of 1011-1012 cm-2 as determined by TEM. We estimate the influence of the incoherent twin boundaries on the electrical transport properties by adapting Read's model of charged dislocations. Our calculations quantitatively confirm that the mobility reduction and collapse as well as partly the compensation are due to the presence of twin lamellae.

  3. Risk and Resilience Factors in Coping with Daily Stress in Adulthood: The Role of Age, Self-Concept Incoherence, and Personal Control

    Science.gov (United States)

    Diehl, Manfred; Hay, Elizabeth L.

    2010-01-01

    This study observed young, middle-aged, and older adults (N = 239; M[subscript age] = 49.6 years; range = 18-89 years) for 30 consecutive days to examine the association between daily stress and negative affect, taking into account potential risk (i.e., self-concept incoherence) and resilience (i.e., age, perceived personal control) factors.…

  4. A Study on Various Meteoroid Disintegration Mechanisms as Observed from the Resolute Bay Incoherent Scatter Radar (RISR)

    Science.gov (United States)

    Malhotra, A.; Mathews, J. D.

    2011-01-01

    There has been much interest in the meteor physics community recently regarding the form that meteoroid mass flux arrives in the upper atmosphere. Of particular interest are the relative roles of simple ablation, differential ablation, and fragmentation in the meteoroid mass flux observed by the Incoherent Scatter Radars (ISR). We present here the first-ever statistical study showing the relative contribution of the above-mentioned three mechanisms. These are also one of the first meteor results from the newly-operational Resolute Bay ISR. These initial results emphasize that meteoroid disintegration into the upper atmosphere is a complex process in which all the three above-mentioned mechanisms play an important role though fragmentation seems to be the dominant mechanism. These results prove vital in studying how meteoroid mass is deposited in the upper atmosphere which has important implications to the aeronomy of the region and will also contribute in improving current meteoroid disintegration/ablation models.

  5. Impact parameter analysis of coherent and incoherent pion production on nuclei by 11.7GeV/c π+

    International Nuclear Information System (INIS)

    Arnold, R.; Barshay, S.; Riester, J.L.

    1976-01-01

    Using the complete momentum measurements for 2, 3, 4 and 5 pion final states. The impact parameter structure, with the following principal results has been studied. Evidence is presented for an empirical method that can help in the separation of coherent events on nuclei. Incoherent nuclear production exhibits lower-bound impact parameters which decrease systematically with an increasing number of produced pions. The experimental b-distributions can be very well fitted by a single simple scaled functional form, dsigmasub(N)(b)/d 2 bvector proportional to F(N/f(b)), this N-distribution yields a ratio (dispersion/average dispersion) of about 0.35 at any impact parameter [fr

  6. F-region electron density and Te / Ti measurements using incoherent scatter power data collected at ALTAIR

    Directory of Open Access Journals (Sweden)

    M. Milla

    2006-07-01

    Full Text Available The ALTAIR UHF radar was used in an incoherent scatter experiment to observe the low-latitude ionosphere during the Equis 2 rocket campaign. The measurements provided the first high-resolution electron density maps of the low-latitude D- and E-region in the Pacific sector and also extended into the F-region and topside ionosphere. Although the sampling frequency was well below the Nyquist frequency of F-region returns, we were able to estimate Te / Ti ratio and infer unbiased electron density estimates using a regularized inversion technique described here. The technique exploits magnetic aspect angle dependence of ISR cross-section for Te>Ti.

  7. Performance analysis of incoherent multi-wavelength OCDMA systems under the impact of four-wave mixing.

    Science.gov (United States)

    Dang, Ngoc T; Pham, Anh T

    2010-05-10

    In this paper, we comprehensively analyze the impact of four wave mixing (FWM) on the performance of incoherent multi-wavelength optical code-division multiple-access (MW-OCDMA) systems. We also consider many other interferences and noises, including multiple access interference, optical beating interference, and receiver noise, in the analysis. From the numerical results, we can find the power ranges of different MW-OCDMA systems, in which the impact of FWM is dominant and consequently results in an increase in the bit-error rate of the systems. We also find that the impact of FWM becomes more severe when the frequency spacing is small and/or dispersion-shifted fiber is used. In addition, we quantitatively discuss the impact of FWM on the number of supportable users and power penalty in the MW-OCDMA systems. (c) 2010 Optical Society of America.

  8. [Language disorders in a right frontal lesion in a right-handed patient. Incoherent speech and extravagant paraphasias. Neuropsychologic study].

    Science.gov (United States)

    Guard, O; Fournet, F; Sautreaux, J L; Dumas, R

    1983-01-01

    Clinical, neuropsychological, and CT scan data are reported in a patient with a right prefrontal hematoma following meningeal hemorrhage due to the rupture of an aneurysm of the anterior communicating artery. Over a period of six weeks, before and after surgery, the patient presented a particular type of language disorder characterized by incoherent speech, verbal paraphasias, unexpected or guided along ideic perseverations, emphatic and affected terms, and impossibility of brief responses, particularly in denomination tests. Contrasting with the absurdity of the discourse, the respect of oral comprehension, the absence of grammatical disorders, and the perfect phonemic and phonetic organization provided evidence of the integrity of the linguistic code. The purely semantic disturbance, however, was the cause of the apparent alteration in reasoning and judgment. A major amnestic syndrome was also present. It improved concomitantly with the language disorders. The explanation proposed is that of a disturbance of an attention process and of word selection due to a prefrontal lesion.

  9. Influence of incoherent scattering on stochastic deflection of high-energy negative particle beams in bent crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kirillin, I.V. [Akhiezer Institute for Theoretical Physics, National Science Center ' ' Kharkov Institute of Physics and Technology' ' , Kharkov (Ukraine); Shul' ga, N.F. [Akhiezer Institute for Theoretical Physics, National Science Center ' ' Kharkov Institute of Physics and Technology' ' , Kharkov (Ukraine); V.N. Karazin Kharkov National University, Kharkov (Ukraine); Bandiera, L. [INFN Sezione di Ferrara, Ferrara (Italy); Guidi, V.; Mazzolari, A. [INFN Sezione di Ferrara, Ferrara (Italy); Universita degli Studi di Ferrara, Dipartimento di Fisica e Scienze della Terra, Ferrara (Italy)

    2017-02-15

    An investigation on stochastic deflection of high-energy negatively charged particles in a bent crystal was carried out. On the basis of analytical calculation and numerical simulation it was shown that there is a maximum angle at which most of the beam is deflected. The existence of a maximum, which is taken in the correspondence of the optimal radius of curvature, is a novelty with respect to the case of positively charged particles, for which the deflection angle can be freely increased by increasing the crystal length. This difference has to be ascribed to the stronger contribution of incoherent scattering affecting the dynamics of negative particles that move closer to atomic nuclei and electrons. We therefore identified the ideal parameters for the exploitation of axial confinement for negatively charged particle beam manipulation in future high-energy accelerators, e.g., ILC or muon colliders. (orig.)

  10. Final-state interaction in spin asymmetry and GDH sum rule for incoherent pion production on the deuteron

    International Nuclear Information System (INIS)

    Darwish, E.M.; Arenhoevel, H.; Schwamb, M.

    2003-01-01

    The contribution of incoherent single-pion photoproduction to the spin response of the deuteron, i.e., the asymmetry of the total photoabsorption cross-section with respect to parallel and antiparallel spins of photon and deuteron, is calculated over the region of the Δ-resonance with inclusion of final-state NN and πN rescattering. Sizeable effects, mainly from NN rescattering, are found leading to an appreciable reduction of the spin asymmetry. Furthermore, the contribution to the Gerasimov-Drell-Hearn integral is explicitly evaluated by integration up to a photon energy of 550 MeV. Final-state interaction reduces the value of the integral to about half of the value obtained for the pure impulse approximation. (orig.)

  11. Bidirectional reflectance distribution function of Spectralon white reflectance standard illuminated by incoherent unpolarized and plane-polarized light.

    Science.gov (United States)

    Bhandari, Anak; Hamre, Børge; Frette, Øvynd; Zhao, Lu; Stamnes, Jakob J; Kildemo, Morten

    2011-06-01

    A Lambert surface would appear equally bright from all observation directions regardless of the illumination direction. However, the reflection from a randomly scattering object generally has directional variation, which can be described in terms of the bidirectional reflectance distribution function (BRDF). We measured the BRDF of a Spectralon white reflectance standard for incoherent illumination at 405 and 680 nm with unpolarized and plane-polarized light from different directions of incidence. Our measurements show deviations of the BRDF for the Spectralon white reflectance standard from that of a Lambertian reflector that depend both on the angle of incidence and the polarization states of the incident light and detected light. The non-Lambertian reflection characteristics were found to increase more toward the direction of specular reflection as the angle of incidence gets larger.

  12. Use of intravoxel incoherent motion diffusion-weighted imaging in identifying the vascular and avascular zones of human meniscus.

    Science.gov (United States)

    Guo, Tan; Chen, Juan; Wu, Bing; Zheng, Dandan; Jiao, Sheng; Song, Yan; Chen, Min

    2017-04-01

    To investigate the hypothesis that the intravoxel incoherent motion (IVIM) diffusion-weighted imaging may depict microcirculation of meniscus and the perfusion changes in meniscal disorder. Fifty patients received diffusion-weighted MRI with multiple b-values ranging from 0 to 400 s/mm 2 . The four horns of the menisci were divided into normal, degenerated, and torn groups. IVIM parameters including perfusion fraction (f), pseudo-diffusion coefficient (D*), true diffusion coefficient (D), and the product of f and D* (f D*) of normal meniscal red zone and white zone were derived and compared for microcirculation changes of normal, degenerated, and torn posterior horn of the medial meniscus (PMM). The parameters between red and white zones among the groups were compared. Significant differences were considered when P meniscus and the perfusion changes in meniscal disorder. 3 J. Magn. Reson. Imaging 2017;45:1090-1096. © 2016 International Society for Magnetic Resonance in Medicine.

  13. Paradox of spontaneous cancer regression: implications for fluctuational radiothermy and radiotherapy

    International Nuclear Information System (INIS)

    Roy, Prasun K.; Dutta Majumder, D.; Biswas, Jaydip

    1999-01-01

    Spontaneous regression of malignant tumours without treatment is a most enigmatic phenomenon with immense therapeutic potentialities. We analyse such cases to find that the commonest cause is a preceding episode of high fever-induced thermal fluctuation which produce fluctuation of biochemical and immunological parameters. Using Prigogine-Glansdorff thermodynamic stability formalism and biocybernetic principles, we develop the theoretical foundation of tumour regression induced by thermal, radiational or oxygenational fluctuations. For regression, a preliminary threshold condition of fluctuations is derived, namely σ > 2.83. We present some striking confirmation of such fluctuation-induced regression of various therapy-resistant masses as Ewing tumour, neurogranuloma and Lewis lung carcinoma by utilising σ > 2.83. Our biothermodynamic stability model of malignancy appears to illuminate the marked increase of aggressiveness of mammalian malignancy which occurred around 250 million years ago when homeothermic warm-blooded pre-mammals evolved. Using experimental data, we propose a novel approach of multi-modal hyper-fluctuation therapy involving modulation of radiotherapeutic hyper-fractionation, temperature, radiothermy and immune-status. (author)

  14. Studies of Fluctuation Processes in Nuclear Collisions

    Energy Technology Data Exchange (ETDEWEB)

    Ayik, Sakir [Tennessee Technological Univ., Cookeville, TN (United States). Dept. of Physics

    2016-04-14

    The standard one-body transport approaches have been extensively applied to investigate heavy-ion collision dynamics at low and intermediate energies. At low energies the approach is the mean-field description of the time-dependent Hartree-Fock (TDHF) theory. At intermediate energies the approach is extended by including a collision term, and its application has been carried out mostly in the semi-classical framework of the Boltzmann-Uhling-Uhlenbeck (BUU) model. The standard transport models provide a good understanding of the average properties of the collision dynamics in terms of the effective interactions in both low and intermediate energies. However, the standard models are inadequate for describing the fluctuation dynamics of collective motion at low energies and disassembling of the nuclear system into fragments at intermediate energies resulting from the growth of density fluctuations in the spinodal region. Our tasks have been to improve the standard transport approaches by incorporating fluctuation mechanisms into the description. There are mainly two different mechanisms for fluctuations: (i) Collisional fluctuations generated by binary nucleon collisions, which provide the dominant mechanism at intermediate energies, and (ii) One-body mechanism or mean-field fluctuations, which is the dominant mechanism at low energies. In the first part of our project, the PI extended the standard transport model at intermediate energies by incorporating collisional mechanism according to the “Generalized Langevin Description” of Mori formalism. The PI and his collaborators carried out a number of applications for describing dynamical mechanism of nuclear multi fragmentations, and nuclear collective response in the semi-classical framework of the approach, which is known as the Boltzmann-Langevin model. In the second part of the project, we considered dynamical description at low energies. Because of the effective Pauli blocking, the collisional dissipation and

  15. Proof of the Feasibility of Coherent and Incoherent Schemes for Pumping a Gamma-Ray Laser

    Science.gov (United States)

    1990-03-01

    from a Varian CLINAC 1800 linear accelera- tor normally employed for radiation therapy treatments. Unfortunately, such bremsstrahlung sources are...sources cause the driving forces depended only upon the value of could give a resulting modulation of 4m2 in a magneto . applied field uoH. In 1984, we...modulation effects propagated by magneto - Nor coisld they be observed at the remote sampling point static waves with the null level of acoustic noise

  16. Nasopharyngeal carcinoma: comparison of diffusion and perfusion characteristics between different tumour stages using intravoxel incoherent motion MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Vincent; Li, Xiao; Huang, Bingsheng; Khong, Pek Lan [University of Hong Kong, Queen Mary Hospital, Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, Hong Kong (China); Lee, Victor Ho Fun; Lam, Ka On [University of Hong Kong, Queen Mary Hospital, Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, Hong Kong (China); Fong, Daniel Yee Tak [University of Hong Kong, School of Nursing, Li Ka Shing Faculty of Medicine, Hong Kong (China); Chan, Queenie [Philips Healthcare, Hong Kong, New Territories (China)

    2014-01-15

    To explore intravoxel incoherent motion (IVIM) characteristics of nasopharyngeal carcinoma (NPC) and relationships with different tumour stages. We prospectively recruited 80 patients with newly diagnosed undifferentiated NPC. Diffusion-weighted MR imaging was performed and IVIM parameters (D, pure diffusion; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated. Patients were stratified into low and high tumour stage groups based on American Joint Committee on Cancer (AJCC) and TNM staging for determination of the predictive powers of IVIM parameters using t test, multiple logistic regression and ROC curve analyses. D, f and D* were all statistically significantly lower in high-stage groups in AJCC, T and N staging. D, f and D* were all independent predictors of AJCC staging, f and D* were independent predictors of T staging, and D was an independent predictor of N staging. D was most powerful for AJCC and N staging, whereas f was most powerful for T staging. Optimal cut-off values (area under the curve, sensitivity, specificity, positive likelihood ratio, negative likelihood ratio) were as follows: AJCC stage, D = 0.782 x 10{sup -3} mm{sup 2}/s (0.915, 93.3 %, 76.2 %, 3.92, 0.09); T staging, f = 0.133 (0.905, 80.5 %, 92.5 %, 10.73, 0.21); N staging, D = 0.761 x 10{sup -3} mm{sup 2}/s (0.848, 87.5 %, 66.7 %, 2.62, 0.19). Multivariate analysis showed no diagnostic improvement. Nasopharyngeal carcinoma has distinctive intravoxel incoherent motion characteristics parameters in different tumour staging, potentially helping pretreatment staging. (orig.)

  17. Active control on high-order coherence and statistic characterization on random phase fluctuation of two classical point sources.

    Science.gov (United States)

    Hong, Peilong; Li, Liming; Liu, Jianji; Zhang, Guoquan

    2016-03-29

    Young's double-slit or two-beam interference is of fundamental importance to understand various interference effects, in which the stationary phase difference between two beams plays the key role in the first-order coherence. Different from the case of first-order coherence, in the high-order optical coherence the statistic behavior of the optical phase will play the key role. In this article, by employing a fundamental interfering configuration with two classical point sources, we showed that the high- order optical coherence between two classical point sources can be actively designed by controlling the statistic behavior of the relative phase difference between two point sources. Synchronous position Nth-order subwavelength interference with an effective wavelength of λ/M was demonstrated, in which λ is the wavelength of point sources and M is an integer not larger than N. Interestingly, we found that the synchronous position Nth-order interference fringe fingerprints the statistic trace of random phase fluctuation of two classical point sources, therefore, it provides an effective way to characterize the statistic properties of phase fluctuation for incoherent light sources.

  18. Theory of relativistic radiation reflection from plasmas

    Science.gov (United States)

    Gonoskov, Arkady

    2018-01-01

    We consider the reflection of relativistically strong radiation from plasma and identify the physical origin of the electrons' tendency to form a thin sheet, which maintains its localisation throughout its motion. Thereby, we justify the principle of relativistic electronic spring (RES) proposed in [Gonoskov et al., Phys. Rev. E 84, 046403 (2011)]. Using the RES principle, we derive a closed set of differential equations that describe the reflection of radiation with arbitrary variation of polarization and intensity from plasma with an arbitrary density profile for an arbitrary angle of incidence. We confirm with ab initio PIC simulations that the developed theory accurately describes laser-plasma interactions in the regime where the reflection of relativistically strong radiation is accompanied by significant, repeated relocation of plasma electrons. In particular, the theory can be applied for the studies of plasma heating and coherent and incoherent emissions in the RES regime of high-intensity laser-plasma interaction.

  19. Properties of auroral kilometric radiation from an interferometer analysis of the ISEE-1 and -2 plasma wave data

    International Nuclear Information System (INIS)

    Baumback, M.M.

    1986-01-01

    The first satellite-satellite interferometery measurements of the auroral kilometric radiation (AKR) source region diameter are presented. By correlating the analog waveforms detected by ISEE-1 and ISEE-2, the size of the AKR source region is determined. Correlations have been measured at 125 and 250 kHz for projected baselines ranging from 20 to 3868 km. High correlations are found at all projected baselines, with little or no tendency to decrease at long baselines. The correlation is lower for events with wide bandwidths than for events with narrow bandwidths. The magnitude of the correlation as a function of signal delay and the spectra of the individual bursts show that sometimes the bandwidth of AKR bursts varies rapidly and can be narrower than 20 Hz. The spectra observed by both spacecraft are nearly identical. Correlation results are interpreted differently for incoherent radiation than for coherent radiation. If the radiation is incoherent, the visibility of the source region is the Fourier transform of the brightness distribution. Assuming incoherent radiation the average source region diameter for all analyzed bursts is less than 9.27 km. Source region diameters measured for individual bursts range from 1 to 16 km. Generation mechanisms that only amplify incoming radiation cannot produce high correlations unless the source region diameter is smaller than 25 km

  20. Correlation length of magnetosheath fluctuations: Cluster statistics

    Directory of Open Access Journals (Sweden)

    O. Gutynska

    2008-09-01

    Full Text Available Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD models but these models cannot account for one of the most important sources of magnetosheath fluctuations – the foreshock. Earlier statistical processing of a large amount of magnetosheath observations has shown that the magnetosheath magnetic field and plasma flow fluctuations downstream of the quasiparallel shock are much larger than those at the opposite flank. These studies were based on the observations of a single spacecraft and thus they could not provide full information on propagation of the fluctuations through the magnetosheath.

    We present the results of a statistical survey of the magnetosheath magnetic field fluctuations using two years of Cluster observations. We discuss the dependence of the cross-correlation coefficients between different spacecraft pairs on the orientation of the separation vector with respect to the average magnetic field and plasma flow vectors and other parameters. We have found that the correlation length does not exceed ~1 RE in the analyzed frequency range (0.001–0.125 Hz and does not depend significantly on the magnetic field or plasma flow direction. A close connection of cross-correlation coefficients computed in the magnetosheath with the cross-correlation coefficients between a solar wind monitor and a magnetosheath spacecraft suggests that solar wind structures persist on the background of magnetosheath fluctuations.

  1. General description of magnetic fluctuations in TEXT

    International Nuclear Information System (INIS)

    Kim, Y.J.

    1989-01-01

    The magnetic fluctuations in TEXT (R = 1m, a = 0.26m, ohmically heated tokamak with a full poloidal limiter) have been extensively measured with magnetic probes in the shadow of the limiter with an instrumental range of f -1 (m rms p (f > 50kHz) at the limiter radius is found to be of order 10 -5 T, which is too small to produce significant transport directly. Over the range of discharge parameters in TEXT, the B rms p (f > 50kHz) is observed to have a strong q a dependence (q a -2.2 ) and also a density dependence (n eo -0.8 ). Furthermore, the magnetic fluctuations show a significant correlation with edge electrostatic density fluctuations measured by Langmiur probe inside the limiter radius, and extending along magnetic field lines. Phase variation of the correlated components suggests k double-prime/k perpendicular ∼ 0.005. The B p rms (f >50kHz) is also found to be little dependent on parallel electric field E double-prime. Magnetic fluctuations in both low and high frequency ranges have been characterized by their response to gas puffing, pellet injection, impurity injection, and the effect of an ergodic magnetic limiter. The behavior of magnetic fluctuations with electron cyclotron resonance heating (ECRH) has been also investigated in detail

  2. Remarks on transport theories of interplanetary fluctuations

    International Nuclear Information System (INIS)

    Ye Zhou; Matthaeus, W.H.

    1990-01-01

    The structure of approximate transport theories for the radial behavior of interplanetary fluctuations is reconsidered. The emphasis is on theories derived under the assumption of scale separation; i.e., the correlation length of the fluctuations is much less than the scale of large inhomogeneities. In these cases the zero-wavelength limit provides a first approximation to the spectral evolution equations for the radial dependence of interplanetary fluctuation spectra. The goal here is to investigate the structure of a recently presented (Zhou and Matthaeus, 1989) transport theory, in which coupling of inward- and outward-type fluctuations appears in the leading order, an effect the authors call mixing. In linear theory, mixing-type couplings of inward-type and outward-type waves are formally a nonresonant effect. However, leading order mixing terms do not vanish at zero wavelength for fluctuations that vary nearly perpendicular to the local magnetic field, or when the mean magnetic field is weak. Leading order mixing terms also survive when the dispersion relation fails and there is a nonunique relationship between frequency and wave number. The former case corresponds to nearly two-dimensional structures; these are included, for example, in isotropic models of turbulence. The latter instance occurs when wave-wave couplings are sufficiently strong. Thus there are a variety of situations in which leading order mixing effects are expected to be present

  3. Correlation length of magnetosheath fluctuations: Cluster statistics

    Directory of Open Access Journals (Sweden)

    O. Gutynska

    2008-09-01

    Full Text Available Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD models but these models cannot account for one of the most important sources of magnetosheath fluctuations – the foreshock. Earlier statistical processing of a large amount of magnetosheath observations has shown that the magnetosheath magnetic field and plasma flow fluctuations downstream of the quasiparallel shock are much larger than those at the opposite flank. These studies were based on the observations of a single spacecraft and thus they could not provide full information on propagation of the fluctuations through the magnetosheath. We present the results of a statistical survey of the magnetosheath magnetic field fluctuations using two years of Cluster observations. We discuss the dependence of the cross-correlation coefficients between different spacecraft pairs on the orientation of the separation vector with respect to the average magnetic field and plasma flow vectors and other parameters. We have found that the correlation length does not exceed ~1 RE in the analyzed frequency range (0.001–0.125 Hz and does not depend significantly on the magnetic field or plasma flow direction. A close connection of cross-correlation coefficients computed in the magnetosheath with the cross-correlation coefficients between a solar wind monitor and a magnetosheath spacecraft suggests that solar wind structures persist on the background of magnetosheath fluctuations.

  4. Fluctuation characteristics in detached recombining plasmas

    International Nuclear Information System (INIS)

    Ohno, Noriyasu; Tanaka, Naoyuki; Takamura, Shuichi; Budaev, Viatcheslav

    2002-01-01

    Fluctuation in detached recombining plasmas has been investigated experimentally in the linear divertor plasma simulator, NAGDIS-II. As increasing neutral gas pressure, floating potential fluctuation of the target plate installed at the end of the NADIS-II device becomes larger and bursty negative spikes are observed in the signal associated with a transition from attached to detached a plasmas. The fluctuation property has been analyzed by using Fast Fourier Transform (FFT), probability distribution function (PDF) and wavelet transform. The PDF of the floating potential fluctuation in the attached plasma condition obeys the Gaussian distribution function, on the other hand, the PDF in detached plasma shows a strong deviation from the Gaussian distribution function, which can be characterized by flatness and skewness. Comparison of the fluctuation properties between the floating potential and the optical emission from the detached plasma has been done based on the wavelet transform to show that a strong correlation between them, which could indicate bursty transport of energetic electrons from upstream to downstream region along the magnetic field. (author)

  5. Biophysical radiation effects

    International Nuclear Information System (INIS)

    Fidorra, J.

    1982-07-01

    The biological effectiveness of ionizing radiation is based upon the absorption of energy in molecular structures of a cell. Because of the quantum nature of radiation large fluctuations of energy concentration in subcellulare regions has to be considered. In addition both the spatial distribution of a sensitive molecular target and cellulare repair processes has to be taken into consideration for an assessment of radiation action. In radiation protection the difference between the quality factor and the Relative Biological Effectiveness has a fundamental meaning and will be discussed in more detail. The present report includes a short review on some relevant models on radiation action and a short discussion on effects of low dose irradiation. (orig.) [de

  6. Magnetosheath density fluctuations and magnetopause motion

    Energy Technology Data Exchange (ETDEWEB)

    Sibeck, D.G. [Johns Hopkins Univ. Applied Physics Lab., Laurel, MD (United States); Gosling, J.T. [Los Alamos National Lab., NM (United States)

    1996-01-01

    The interplanetary magnetic field (IMF) orientation controls foreshock densities and modulates the fraction of the solar wind dynamic pressure applied to the magnetosphere. Such pressure variations produce bow shock and magnetopause motion and cause the radial profiles for various magnetosheath parameters to sweep inward and outward past nearly stationary satellites. The authors report ISEE 2 observations of correlated density and speed fluctuations, and anticorrelated density and temperature fluctuations, on an outbound pass through the northern dawnside magnetosheath. Densities decreased when the magnetic field rotated southward and draped about the magnetopause. In the absence of any significant solar wind density or dynamic pressure variations, they interpret the magnetosheath fluctuations as evidence for radial magnetosheath motion induced by variations in the IMF orientation. 41 refs., 8 figs.

  7. Fluctuation effects in bulk polymer phase behavior

    International Nuclear Information System (INIS)

    Bates, F.S.; Rosedale, J.H.; Stepanek, P.; Lodge, T.P.; Wiltzius, P.; Hjelm R, Jr.; Fredrickson, G.H.

    1990-01-01

    Bulk polymer-polymer, and block copolymer, phase behaviors have traditionally been interpreted using mean-field theories. Recent small-angle neutron scattering (SANS) studies of critical phenomena in model binary polymer mixtures confirm that non-mean-field behavior is restricted to a narrow range of temperatures near the critical point, in close agreement with the Ginzburg criterion. In contrast, strong derivations from mean-field behavior are evident in SANS and rheological measurements on model block copolymers more than 50C above the order-disorder transition (ODT), which can be attributed to sizeable composition fluctuations. Such fluctuation effects undermine the mean-field assumption, conventionally applied to bulk polymers, and result in qualitative changes in phase behavior, such as the elimination of a thermodynamic stability limit in these materials. The influence of fluctuation effects on block copolymer and binary mixture phase behavior is compared and contrasted in this presentation

  8. Classical and quantum temperature fluctuations via holography

    Energy Technology Data Exchange (ETDEWEB)

    Balatsky, Alexander V. [KTH Royal Inst. of Technology, Stockholm (Sweden); Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gudnason, Sven Bjarke [KTH Royal Inst. of Technology, Stockholm (Sweden); Thorlacius, Larus [KTH Royal Inst. of Technology, Stockholm (Sweden); University of Iceland, Reykjavik (Iceland); Zarembo, Konstantin [KTH Royal Inst. of Technology, Stockholm (Sweden); Inst. of Theoretical and Experimental Physics (ITEP), Moscow (Russian Federation); Uppsala Univ. (Sweden); Krikun, Alexander [KTH Royal Inst. of Technology, Stockholm (Sweden); Inst. of Theoretical and Experimental Physics (ITEP), Moscow (Russian Federation); Kedem, Yaron [KTH Royal Inst. of Technology, Stockholm (Sweden)

    2014-05-27

    We study local temperature fluctuations in a 2+1 dimensional CFT on the sphere, dual to a black hole in asymptotically AdS space-time. The fluctuation spectrum is governed by the lowest-lying hydrodynamic sound modes of the system whose frequency and damping rate determine whether temperature fluctuations are thermal or quantum. We calculate numerically the corresponding quasinormal frequencies and match the result with the hydrodynamics of the dual CFT at large temperature. As a by-product of our analysis we determine the appropriate boundary conditions for calculating low-lying quasinormal modes for a four-dimensional Reissner-Nordstrom black hole in global AdS.

  9. Stochastic dark energy from inflationary quantum fluctuations

    Science.gov (United States)

    Glavan, Dražen; Prokopec, Tomislav; Starobinsky, Alexei A.

    2018-05-01

    We study the quantum backreaction from inflationary fluctuations of a very light, non-minimally coupled spectator scalar and show that it is a viable candidate for dark energy. The problem is solved by suitably adapting the formalism of stochastic inflation. This allows us to self-consistently account for the backreaction on the background expansion rate of the Universe where its effects are large. This framework is equivalent to that of semiclassical gravity in which matter vacuum fluctuations are included at the one loop level, but purely quantum gravitational fluctuations are neglected. Our results show that dark energy in our model can be characterized by a distinct effective equation of state parameter (as a function of redshift) which allows for testing of the model at the level of the background.

  10. Force fluctuations assist nanopore unzipping of DNA

    International Nuclear Information System (INIS)

    Viasnoff, V; Chiaruttini, N; Muzard, J; Bockelmann, U

    2010-01-01

    We experimentally study the statistical distributions and the voltage dependence of the unzipping time of 45 base-pair-long double-stranded DNA through a nanopore. We then propose a quantitative theoretical description considering the nanopore unzipping process as a random walk of the opening fork through the DNA sequence energy landscape biased by a time-fluctuating force. To achieve quantitative agreement fluctuations need to be correlated over the millisecond range and have an amplitude of order k B T/bp. Significantly slower or faster fluctuations are not appropriate, suggesting that the unzipping process is efficiently enhanced by noise in the kHz range. We further show that the unzipping time of short 15 base-pair hairpins does not always increase with the global stability of the double helix and we theoretically study the role of DNA elasticity on the conversion of the electrical bias into a mechanical unzipping force.

  11. Maxwell electrodynamics subjected to quantum vacuum fluctuations

    International Nuclear Information System (INIS)

    Gevorkyan, A. S.; Gevorkyan, A. A.

    2011-01-01

    The propagation of electromagnetic waves in the vacuum is considered taking into account quantum fluctuations in the limits of Maxwell-Langevin (ML) equations. For a model of “white noise” fluctuations, using ML equations, a second order partial differential equation is found which describes the quantum distribution of virtual particles in vacuum. It is proved that in order to satisfy observed facts, the Lamb Shift etc, the virtual particles should be quantized in unperturbed vacuum. It is shown that the quantized virtual particles in toto (approximately 86 percent) are condensed on the “ground state” energy level. It is proved that the extension of Maxwell electrodynamics with inclusion of the vacuum quantum field fluctuations may be constructed on a 6D space-time continuum with a 2D compactified subspace. Their influence on the refraction indexes of vacuum is studied.

  12. Simultaneous measurement of 3 fluctuating plasma parameters

    International Nuclear Information System (INIS)

    Carlson, A.; Giannone, L.

    1991-01-01

    Langmuir triple probes can provide simultaneous measurements of n e , T e and V pl with good temporal and spatial resolution, and therefore are especially suited to detailed investigations of plasma turbulence in the scrape-off-layer. Unfortunately, the finite tip separation coupled with the fluctuating gradients prevents a simple interpretation of the results. We have developed a method using, essentially, two or more triple probes, which allows a good estimate of the three plasma parameters and their spatial derivatives at each point of time (assuming tip separation is much less than correlation length and dimensionless fluctuation levels are much less than unity). In particular, we can unambiguously measure the temperature fluctuations and the turbulent particle and heat flux. (author) 1 fig

  13. Simultaneous measurement of 3 fluctuating plasma parameters

    International Nuclear Information System (INIS)

    Carlson, A.; Giannone, L.

    1991-01-01

    Langmuir triple probes can provide simultaneous measurements of n e , T e , and V pl with good temporal and spatial resolution, and therefore are especially suited to detailed investigations of plasma turbulence in the scrape-off-layer. Unfortunately, the finite tip separation coupled with the fluctuating gradients prevents a simple interpretation of the results. We have developed a method using, essentially, two or more triple probes, which allows a good estimate of the three plasma parameters and their spatial derivatives at each point of time (assuming tip separation is much less than correlation length and dimensionless fluctuation levels are much less than unity). In particular, we can unambiguously measure the temperature fluctuations and the turbulent particle and heat flux. (orig.)

  14. Simultaneous measurement of 3 fluctuating plasma parameters

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, A; Giannone, L. (Max-Planck-Institut fuer Plasmaphysik, Garching (Germany))

    1991-01-01

    Langmuir triple probes can provide simultaneous measurements of n[sub e], T[sub e] and V[sub pl] with good temporal and spatial resolution, and therefore are especially suited to detailed investigations of plasma turbulence in the scrape-off-layer. Unfortunately, the finite tip separation coupled with the fluctuating gradients prevents a simple interpretation of the results. We have developed a method using, essentially, two or more triple probes, which allows a good estimate of the three plasma parameters and their spatial derivatives at each point of time (assuming tip separation is much less than correlation length and dimensionless fluctuation levels are much less than unity). In particular, we can unambiguously measure the temperature fluctuations and the turbulent particle and heat flux. (author) 1 fig.

  15. RSA fluctuation in major depressive disorder.

    Science.gov (United States)

    Rottenberg, Jonathan; Clift, April; Bolden, Sarah; Salomon, Kristen

    2007-05-01

    Cardiac vagal control, as measured by indices of respiratory sinus arrhythmia (RSA), has been investigated as a marker of impaired self-regulation in mental disorders, including depression. Past work in depressed samples has focused on deficits in resting RSA levels, with mixed results. This study tested the hypothesis that depression involves abnormal RSA fluctuation. RSA was measured in depressed and healthy control participants during rest and during two reactivity tasks, each followed by a recovery period. Relative to controls, depressed persons exhibited lower resting RSA levels as well as less RSA fluctuation, primarily evidenced by a lack of task-related vagal suppression. Group differences in RSA fluctuation were not accounted for by differences in physical health or respiration, whereas group differences in resting RSA level did not survive covariate analyses. Depression may involve multiple deficits in cardiac vagal control.

  16. Mesoscale wind fluctuations over Danish waters

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, C.L.

    2010-12-15

    Mesoscale wind fluctuations affect the large scale integration of wind power because they undermine the day-ahead predictability of wind speed and power production, and because they can result in large fluctuations in power generation that must be balanced using reserve power. Large fluctuations in generated power are a particular problem for offshore wind farms because the typically high concentration of turbines within a limited geographical area means that fluctuations can be correlated across large numbers of turbines. Furthermore, organised mesoscale structures that often form over water, such as convective rolls and cellular convection, have length scales of tens of kilometers, and can cause large wind fluctuations on a time scale of around an hour. This thesis is an exploration of the predictability of mesoscale wind fluctuations using observations from the world's first two large offshore wind farms - Horns Rev I in the North Sea, and Nysted in the Baltic Sea. The thesis begins with a climatological analysis of wind fluctuations on time scales of 1-10 hours at the two sites. A novel method for calculating conditional climatologies of spectral information is proposed, based on binning and averaging the time axis of the Hilbert spectrum. Results reveal clear patterns between wind fluctuations and locally observed meteorological conditions. The analysis is expanded by classifying wind fluctuations on time scales of 1-3 hours according to synoptic patterns, satellite pictures and wind classes. Results indicate that cold air outbreaks and open cellular convection are a significant contributor to mesoscale wind variability at Horns Rev. The predictability of mesoscale wind fluctuations is tested by implementing standard statistical models that relate local wind variability to parameters based on a large scale weather analysis. The models show some skill, but only achieve a 15% improvement on a persistence forecast. The possibility of explicitly modelling

  17. Fluctuation diamagnetism in two-band superconductors

    Science.gov (United States)

    Adachi, Kyosuke; Ikeda, Ryusuke

    2016-04-01

    Anomalously large fluctuation diamagnetism around the superconducting critical temperature has been recently observed in iron selenide (FeSe) [Kasahara et al. (unpublished)]. This indicates that superconducting fluctuations (SCFs) play a more significant role in FeSe, which supposedly has a two-band structure, than in the familiar single-band superconductors. Motivated by the data on FeSe, SCF-induced diamagnetism is examined in a two-band system, on the basis of a phenomenological approach with a Ginzburg-Landau functional. The obtained results indicate that the SCF-induced diamagnetism may be more enhanced than that in a single-band system due to the existence of two distinct fluctuation modes. Such enhancement of diamagnetism unique to a two-band system seems consistent with the large diamagnetism observed in FeSe, though still far from a quantitative agreement.

  18. Extracellular matrix fluctuations during early embryogenesis

    International Nuclear Information System (INIS)

    Szabó, A; Rupp, P A; Rongish, B J; Little, C D; Czirók, A

    2011-01-01

    Extracellular matrix (ECM) movements and rearrangements were studied in avian embryos during early stages of development. We show that the ECM moves as a composite material, whereby distinct molecular components as well as spatially separated layers exhibit similar displacements. Using scanning wide field and confocal microscopy we show that the velocity field of ECM displacement is smooth in space and that ECM movements are correlated even at locations separated by several hundred micrometers. Velocity vectors, however, strongly fluctuate in time. The autocorrelation time of the velocity fluctuations is less than a minute. Suppression of the fluctuations yields a persistent movement pattern that is shared among embryos at equivalent stages of development. The high resolution of the velocity fields allows a detailed spatio-temporal characterization of important morphogenetic processes, especially tissue dynamics surrounding the embryonic organizer (Hensen's node)

  19. Faraday polarization fluctuations of satellite beacon signals

    Science.gov (United States)

    Lee, M. C.; Klobuchar, J. A.

    1988-01-01

    The anisotropic effects of random density irregularities in causing Faraday polarization fluctuations of VHF radio signals are examined, taking both rod-like and sheet-like irregularities into consideration. It is found that the variance of Faraday polarization fluctuations depends on the ratio of perpendicular to parallel correlation lengths. The anisotropic effect of rod-like ionospheric irregularities are shown to be most appreciable for longitudinal propagation. The anisotropic effect of sheet-like ionospheric irregularities, however, is not strongly dependent on the radio propagation angle. During transionospheric propagation at large angles with respect to the geomagnetic field, sheet-like irregularities may cause greater Faraday polarization fluctuations than rod-like irregularities.

  20. Inverse scattering problem in turbulent magnetic fluctuations

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2016-08-01

    Full Text Available We apply a particular form of the inverse scattering theory to turbulent magnetic fluctuations in a plasma. In the present note we develop the theory, formulate the magnetic fluctuation problem in terms of its electrodynamic turbulent response function, and reduce it to the solution of a special form of the famous Gelfand–Levitan–Marchenko equation of quantum mechanical scattering theory. The last of these applies to transmission and reflection in an active medium. The theory of turbulent magnetic fluctuations does not refer to such quantities. It requires a somewhat different formulation. We reduce the theory to the measurement of the low-frequency electromagnetic fluctuation spectrum, which is not the turbulent spectral energy density. The inverse theory in this form enables obtaining information about the turbulent response function of the medium. The dynamic causes of the electromagnetic fluctuations are implicit to it. Thus, it is of vital interest in low-frequency magnetic turbulence. The theory is developed until presentation of the equations in applicable form to observations of turbulent electromagnetic fluctuations as input from measurements. Solution of the final integral equation should be done by standard numerical methods based on iteration. We point to the possibility of treating power law fluctuation spectra as an example. Formulation of the problem to include observations of spectral power densities in turbulence is not attempted. This leads to severe mathematical problems and requires a reformulation of inverse scattering theory. One particular aspect of the present inverse theory of turbulent fluctuations is that its structure naturally leads to spatial information which is obtained from the temporal information that is inherent to the observation of time series. The Taylor assumption is not needed here. This is a consequence of Maxwell's equations, which couple space and time evolution. The inversion procedure takes